Last updated: March 2021 

Over the last few months, we have been gathering questions about COVID-19 vaccines from our local community. Imperial researchers and Imperial NHS Trust clinicians working in this area have been answering and we've collected them here - thank you to all of those who have helped. 

Please keep in mind that all these answers are based on what we know at the time of writing, using available data and following current NHS guidance.

General questions

People who have had COVID-19 disease (either confirmed or suspected) should still have the COVID-19 vaccine. There is no evidence of safety concerns for vaccinating individuals with a history of COVID-19 infection, or who have COVID-19 antibodies. 

Unfortunately, we can’t comment on any of the logistics surrounding the vaccine rollout, as this is not our area of expertise.  

However, our clinical colleagues in the Imperial NHS Trust advised the below in terms of the timeframe between doses, which you may find helpful:  

All the approved vaccines provide the best protection when two doses have been given. When the vaccines were developed and tested, they were tested with a 3–4-week interval between dose 1 and dose 2. We know that this timeframe works well, because this was the timeframe used in the clinical trials. NHS policy at the moment is for dose 2 to be given within 12 weeks of receiving dose 1. 

This is because the NHS is following Government's expert advisers who say that prioritising a first dose for as many people as possible will save more lives. Even with just one dose, the Pfizer/BioNTech vaccine has been estimated to offer 89% effectiveness* from two weeks after it is given, and the Oxford/AstraZeneca has been estimated to offer 74% effectiveness* from two weeks after it is given. 

As the Deputy Chief Medical Officer, Jonathan Van Tam, has said: “The evidence clearly shows vaccinated individuals get almost complete protection after the first dose. Simply put, every time we vaccinate someone a second time, we are not vaccinating someone else for the first time. It means we are missing an opportunity to greatly reduce the chances of the most vulnerable people getting severely ill from Covid-19. If a family has two elderly grandparents and there are two vaccines available, it is better to give both 89 per cent than to give one 95 per cent protection with two quick doses, and the other grandparent no protection at all.” 

When the number of people suffering in hospital is much lower, we would expect the interval between doses to return to that indicated by the clinical trial (3-4 weeks). 

*Efficacy and effectiveness are two different things: 

  • The efficacy of the vaccine relates to how it works in a clinical trial situation. These are highly controlled environments where many different variables are monitored by scientists. 

  • The effectiveness of the vaccine relates to how it works in a real-life situation – I.e. when it is actually rolled out to the general population. 

The best vaccine to have is the one you are offered – they have been deemed safe and effective. 

There’s more to a vaccine’s impact than its efficacy. Check out this video - https://www.youtube.com/watch?v=p7Ond40hu1k 

The most up-to-date information on who is being offered a vaccine can be found on the NHS website. At time of writing, vaccines being offered to: 

  • people aged 55 and over 

  • people who are at high risk from coronavirus (clinically extremely vulnerable) 

  • people who are at moderate risk from coronavirus (clinically vulnerable) 

  • people who live or work in care homes 

  • health and social care workers 

  • people with a condition that puts them at higher risk (clinically vulnerable) 

  • people with a learning disability 

  • people who are a main carer for someone at high risk from coronavirus 

 

Clinically Extremely Vulnerable (CEV) list: 

 

  • you've had an organ transplant 

  • you're having chemotherapy or antibody treatment for cancer, including immunotherapy 

  • you're having an intense course of radiotherapy (radical radiotherapy) for lung cancer 

  • you're having targeted cancer treatments that can affect the immune system (such as protein kinase inhibitors or PARP inhibitors) 

  • you have blood or bone marrow cancer (such as leukaemia, lymphoma or myeloma) 

  • you've had a bone marrow or stem cell transplant in the past 6 months, or are still taking immunosuppressant medicine 

  • you've been told by a doctor you have a severe lung condition (such as cystic fibrosis, severe asthma or severe COPD) 

  • you have a condition that means you have a very high risk of getting infections (such as SCID or sickle cell) 

  • you're taking medicine that makes you much more likely to get infections (such as high doses of steroids or immunosuppressant medicine) 

  • you have a serious heart condition and are pregnant 

  • you have a problem with your spleen or your spleen has been removed (splenectomy) 

  • you're an adult with Down's syndrome 

  • you're an adult who is having dialysis or has severe (stage 5) long-term kidney disease 

The COVID-19 vaccines will protect against the disease and reduce your chance of becoming seriously ill with COVID-19. This has been found through trials and is being further evidenced as the vaccines are rolled out in the community. They have been approved by the UK regulator MHRA to be safe and effective. The bodies in the UK who review vaccine data (*JCVI) and advise the government, have reviewed the vaccine trial data and decided that the time between the first and second dose can be lengthened. This is in order to vaccinate the greatest number of people in the shortest possible time and therefore have the biggest impact on protecting the population. However, it is still really important that you get the second dose if you are offered it. 

Figures: Pfizer vaccine reported 95% efficacy (that means that in the trial they found a 95% reduction in the number of new cases of the disease in the vaccine group compared with the placebo group). The Astra-Zeneca vaccine was found to prevent around 70% cases in their trials (70% efficacy). Whilst this number is lower than the Pfizer vaccine, there is more to a vaccine’s impact than efficacy. Check out this video. 

*Who are JCVI? The JCVI (Joint Committee on Vaccination and Immunisation) is an independent group of experts who advise Government health departments in the four UK nations on immunisations and the prevention of infectious disease. They consider vaccine safety, efficacy and look at the impact and cost effectiveness of immunisation strategies. The JCVI looks at data on the impact of a disease, data from clinical trials and modelled data, then advises on the best way to get these vaccines to the public. 

Vaccine development

Answer to follow

For both Pfizer and Astra-Zeneca vaccine trials, the participants included people of various ages, immune-compromised and those with underlying health conditions. The efficacy of the vaccine was found through all the subgroups. Vaccine trials on children under 16 years of age are commencing but children were not included in the original trials. 

The only exception is that any person with a history of immediate-onset anaphylaxis (severe allergic reaction) to the ingredients contained in the vaccines should not receive them. 

There is also evidence to show the vaccine is safe for BAME communities: 

  • For the Pfizer trial, participants included 9.6% Black/African, 26.1% Hispanic/Latino and 3.4% Asian.  
  • For the Oxford/AstraZeneca vaccine 10.1% of trial participants were Black and 3.5% Asian.
  • There is no evidence either of the vaccines will work differently in different ethnic groups.  

Trials did include participants from a range of ages. The UK regulators, the EMA and the WHO have examined all the data from the different stages of the vaccine trials, and this showed that the data on immune responses was “very reassuring" for those aged over 65 years. Most importantly all agree it was very safe for each age group. 

 

The development was able to happen quicker than normal as there was a huge global financial and political effort. Additionally, instead of waiting until the end of the trials for the data to be sent to regulators, there was ongoing assessment of data as soon as it became available so regulators could review, ask questions and request extra information as needed throughout the trials rather than afterward. 

There are different types of RNA. RNA vaccines use mRNA (messenger RNA) inside a lipid (fat) membrane. This fatty cover both protects the mRNA when it first enters the body and helps it to get inside cells by fusing with the cell membrane. Once the mRNA is inside the cell, machinery inside the cell translates it into the antigen protein – in this case, the SARS-CoV-2 “spike” protein. This mRNA typically lasts a few days, but in that time sufficient antigen is made to stimulate an immune response. It is then naturally broken down and removed by the body. RNA vaccines are not capable of combining with the human genetic code (DNA).  

There are two RNA vaccines authorised for emergency use in the UK at present. The Pfizer BioNTech and the Moderna COVID-19 vaccines are both RNA vaccines.  

Researchers have been studying and working with mRNA vaccines for decades. Interest has grown in these vaccines because they can be developed in a laboratory using readily available materials. This means the process can be standardized and scaled up, meaning the mRNA vaccine development can happen faster than traditional methods of making vaccines. 

Safety and testing

Yes - the vaccine is safe. The NHS could not offer any COVID-19 vaccines to the public until independent experts have signed off that it is safe. 

The MHRA, the official UK regulator, has said COVID-19 vaccines are safe and highly effective. Vaccines, like any medicine, are highly regulated products. There are checks at every stage in the development and manufacturing process. None of the usual vaccine safety checks or stages have been missed in the development of the COVID-19 vaccines.  

There is also evidence to show the vaccine is safe for BAME communities: 

  • For the Pfizer trial, participants included 9.6% Black/African, 26.1% Hispanic/Latino and 3.4% Asian.   
  • For the Oxford/AstraZeneca vaccine 10.1% of trial recipients were Black and 3.5% Asian. 
  • There is no evidence either of the vaccines will work differently in different ethnic groups. 

The vaccine cannot give you COVID-19 infection. 

These may be helpful resources: 

It is true that we don’t have long-term data, but we have four pieces of reassuring useful information. 

  1. The vaccine trials were started in Summer 2020, so we do now have several months of follow-up data from 23,000 people for the Oxford-AstraZeneca vaccine and 44,000 people for the Pfizer-BioNTech vaccine.  
  2. We know that in most vaccines any side effects are normally experienced immediately after vaccination – in the first few days. So, for COVID-19 we do know that you could get a sore arm, a headache, maybe a low fever and general tiredness after the vaccine but these will resolve and are short-lived. 
  3. We have long-term follow-up for decades of people who have received many different vaccines safely – we can be confident as scientists and members of the public that vaccines as a type of medical intervention are safe and effective which should reassure us all. 
  4. Trial participants continue to be followed up now so that if in the unlikely event any longer-term side effects did occur, they would be quickly investigated. 

 

A core part of the REACT (Real-Time Assessment of Community Transmission) testing programme that is being carried out by us here at Imperial with Ipsos Mori is a nationwide scheme that tests the general public for antibodies. This part of the programme is called REACT-2 and invites a random selection of the population in England to perform a finger-prick antibody test at home in order to test whether they have antibodies against the coronavirus (COVID-19). They then self-report their results via an online survey alongside questions about themselves and recent health/COVID-19 symptoms. The testing has been running since June 2020 with a new round of invites sent out roughly every 6 weeks. While these testing kits are not 100% reliable, when used to test a large number of people in this way, they are reliable enough for us to make a good estimate of the prevalence of antibodies at a population level. 

We can confirm that in light of the vaccination rollout, the REACT-2 survey will now also be asking participants about vaccine uptake, including which vaccine they have received, the number of jabs and date of doses. This will allow us to continue to monitor variations in antibody response, including by age and vaccination status, across England. We have in fact recently edited our invitation letter to encourage people in older age groups to still take part in the study, even if they've had a vaccine, to help us answer this question. 

Other studies of immune response after vaccination are also being performed, for example in healthcare workers, and the Office for National Statistics (ONS) is also carrying out community testing for antibodies, which will likely monitor who has received a vaccine too. 

Vaccine ingredients and suitability

The regulatory bodies (Public Health England, the Joint Committee on Vaccination and Immunisation and the Medicines and Healthcare products Regulatory Agency) have all been very clear that in the absence of trial data to show it is safe and effective, doses should not be mixed.  

If you have a first dose of one vaccine, your second dose will be of that same vaccine too and that is what NHS organisations have been instructed to do. 

We asked Dr Holder, a reproductive immunologist here at Imperial. She said that this question is really interesting, and also difficult to answer because there’s a lot about ethics here. She stressed that it’s up to the individual when making decisions like this, but hoped the below would offer some helpful information:  

The AstraZeneca/Oxford vaccine uses a weakened version of a common cold virus which has been modified to contain the instructions for the coronavirus spike protein in the vaccine. A cell line called HEK 293, derived from a female fetus aborted in the 1970s, was used to grow this weakened version of the common cold virus. (There is a myth circulating online that MRC-5 cells from a male fetus are in the vaccine - this is incorrect. They were used to test the vaccine but are not used in its manufacture).  

The fetal cells are not present in the final product.  

In your question, you were concerned about not ‘benefit’-ing from abortion. We have heard this concern before, whether for religious or personal issues, and you should not feel alone.  

You may benefit from discussing your concerns with your GP, or trusted healthcare professional. Some religious organisations have also issued statements on the issue:  

I think it important to remember that the origin of these HEK 293 cells are a therapeutic abortion around 50 years ago. The abortion did not occur with the purpose or intention of generating vaccines. Receiving the vaccine does not encourage anyone to perform or receive an abortion. Religious institutions have recognized this, for example the statement from the Catholic Church says: “the use of such vaccines does not constitute formal co-operation with the abortion”. 

The other way to look at it is that subsequent cells derived from this fetus over many decades have allowed scientists to protect and preserve millions of lives around the world. Not having the vaccine will not change the past but having it will protect the vaccinated person and the people around them. 

There is no material of foetal or animal origin, including eggs, in either the AstraZeneca or Pfizer COVID-19 vaccines.   

The British Islamic Medical Association recommends people who are eligible have the vaccine and stress that though there is negligible alcohol in it (0.002mg) this is no more than in a slice of bread, for example. (A protein that is made in cells descended from human embryonic cells is in the Astra-Zeneca vaccine however there are NO original or descended cells in the vaccine). 

See the section on “What’s in a vaccine?” on the LSHTM website: 

https://www.lshtm.ac.uk/research/centres/vaccine-centre/vaccine-faqs# 

For full information on ingredients, ask for the Patient Information Leaflet for the vaccine you are offered. Common ingredients used in vaccines, and present in both the Pfizer-BioNTech and Oxford-AstraZeneca vaccines are: 

  • Sucrose (sugar) 
  • Acidity regulators (http://vk.ovg.ox.ac.uk/vk/vaccine-ingredients#acidity%20regulators) such as Histidine, and sodium and potassium salts 

 The active ingredient of the Pfizer-BioNTech vaccine is BNT162b2, which contains the genetic code for the coronavirus spike protein, inside a lipid (fat) capsule. The vaccine also contains other inactive ingredients such as cholesterol.  

The active ingredient of the Oxford-AstraZeneca ChAdOx1 nCoV-19 vaccine is made from a modified adenovirus which causes the common cold in chimpanzees. This virus has been modified so that it cannot cause an infection. It is used to deliver the genetic code for the coronavirus spike protein. The vaccine also contains inactive ingredients such as polysorbate 80, an emulsifier, and a very small amount of alcohol (0.002mg per dose). The vaccine also contains traces of magnesium (3 to 20 parts per million). 

All vaccine ingredients are present in very small amounts and there is no evidence that they can cause harm in these amounts. The Pfizer-BioNTech and Oxford-AstraZeneca vaccines do not contain: 

  • Human or animal products 
  • Common allergens such as latex, milk, lactose, gluten, egg, maize/corn, or peanuts 

The vaccines do not contain a classical adjuvant. Adjuvants are typically included with protein or killed vaccines but, particularly for these RNA vaccines, having an adjuvant may interfere with the expression of the protein from the RNA. And that’s why an additional adjuvant was not included. However, the ball of lipids that encapsulated the RNA does seem to have a small degree of adjuvant effect, the body recognizes the fats (and likely the fats in combination with the RNA) as being different from the rest of the body and so this gives a small stimulation which can be considered as an adjuvant effect. 

Efficacy

It is very important to understand the difference between “efficacy” and “effectiveness”. 

 

The efficacy of the vaccine is related to how it works in a clinical trial situation. These are highly controlled environments where many different variables are controlled and monitored by scientists. 

 

The effectiveness of the vaccine relates to how it works in a real-life situation – when it is actually rolled out to the general population. 

 

So, we get the efficacy from the large phase three clinical trials that we base a lot of the recommendations on, and then we monitor the effectiveness from the information we get after starting to vaccinate the general population (under non-trial situations).  

 

COVID-19 variants

There is no evidence currently that the new strains will be resistant to the vaccines we have, so we are continuing to vaccinate people as normal. Scientists are now looking in detail at the characteristics of the virus in relation to the vaccines. Viruses, such as the winter flu virus, often branch into different strains but these small variations rarely render vaccines ineffective. 

There is still no reason to believe that any new strain will be ‘stronger’, the new variants that we are seeing at the moment, are more infectious but don’t seem to cause significantly more deaths (we will review evidence continuously). But that said – it is very possible that the virus will still be circulating for some years and therefore we may need booster shots. If this does turn out to be the case, the booster could be given annually rather like the Flu shot. 

It's not unexpected that new variants have developed - all viruses mutate as they make copies of themselves to spread and thrive. Most of these differences are inconsequential. A few can even be harmful to the virus's survival. But some can make it more infectious or threatening. 

 

Current vaccines were designed around earlier versions of coronavirus, but scientists believe they should still work against the new ones, although perhaps not quite as well. 

 

Early results suggest the Pfizer vaccine protects against the new variants, but is slightly less effective. 

 

Two new coronavirus vaccines that could be approved soon - one from Novavax and another from Janssen - appear to offer some protection too. 

 

Data from the Oxford-AstraZeneca vaccine team suggests it protects just as well against the new UK variant. It offers less protection against the South Africa variant - although it should still protect against severe illness. 

 

Early results from Moderna suggest its vaccine is effective against the South Africa variant, although the immune response may not be as strong or long-lasting. 

 

Variants could emerge in the future that are more different again. Even in the worst-case scenario, vaccines could be redesigned and tweaked to be a better match - in a matter of weeks or months, if necessary, say experts. As with flu, where a new shot is given each year to account for any changes in circulating flu viruses, something similar could happen for coronavirus. 

Vaccine side effects

Serious allergic reactions to the COVID-19 vaccines are rare. However, the advice for the COVID-19 vaccines is that you should not have the COVID-19 vaccine if you have ever had a serious allergic reaction (including anaphylaxis) to: 

  • a previous dose of the same vaccine 

  • any of the ingredients in the vaccine  

Serious allergic reactions are rare. If you do have a reaction to the vaccine, it usually happens in minutes. Staff giving the vaccine are trained to deal with allergic reactions and treat them immediately. 

MHRA revised its position on 30 December 2020 after careful consideration based on enhanced surveillance of over one million doses of the vaccine in the UK and North America—including in jurisdictions where people with serious allergies were never barred from receiving the vaccine. It found no evidence of an increased risk of anaphylaxis to the Pfizer-BioNTech vaccine among people with serious but unrelated allergy histories and advised that only people who had an allergic reaction to the first dose of this vaccine, or who previously had reactions to any of its components, should not receive it. 

There isn’t a researcher at Imperial College London that is looking specifically at hypertension and vaccine side effects, however our Imperial NHS Trust colleague advised that side effects are usually mild, and that you can find more specific detail here.

The British Heart Foundation have produced this really useful guidance for people with heart conditions, and who might be taking medication related to heart and circulatory conditions. We would recommend you take a look here. 

One part of this guide is particularly relevant: 

The vaccine is safe for people with heart and circulatory conditions. No vaccine will be approved unless it is considered safe for people with long-term conditions, including heart and circulatory conditions, and including older people. The Joint Committee on Vaccination and Immunisation has decided that people who are at risk because of a heart condition should be among those who are prioritised to receive the vaccine. 

As part of the testing, experts looked at whether there are any differences in how well the vaccines work in people with health conditions, and found that they work just as well. In the case of the Pfizer/BioNTech vaccine, there were no meaningful differences in how well it works in people with health conditions that put them at risk of severe COVID-19 (including diabetes, high blood pressure, asthma and obesity.) 

Testing for the Oxford vaccine included people with heart and circulatory disease, diabetes, lung disease and obesity, and found it gave similar levels of protection as to those who did not have those conditions. 

Similarly, the testing for the Moderna vaccine included people with diabetes, significant heart or circulatory disease, chronic lung disease, severe obesity and liver disease. The research found that the vaccine worked similarly well in these higher-risk groups to the general population. 

There is no evidence to suggest this. 

We are unable to comment on whether an individual will get a specific reaction or not. Most side effects of the COVID-19 vaccine are mild and should not last longer than a week such as: sore arm, feeling tired, a headache, feeling achy or feeling or being sick. You can take painkillers such as paracetamol if you need to. 

Although the vaccines were not tested on those with very serious immunological conditions, trial participants included some that were immuno-compromised.  

The vaccines have been proven to be very effective and it is unlikely that a vaccine will have no effect at all on these individuals.  There may be a very small number of people with very complex or severe immunological problems who can’t make any response at all – but the vaccine should not do any harm to these individuals.  

In any case, the best course of action is to discuss the vaccine further with your specialist doctor, who will be able to provide guidance based on the nature of your condition. 

For both Pfizer and AstraZeneca vaccine trials the participants included people of various ages, immune-compromised and those with underlying health conditions. The efficacy of the vaccine was found through all the subgroups.  

The only exception is that any person with a history of immediate-onset anaphylaxis (severe allergic reaction) to the ingredients contained in the vaccines should not receive them. 

There has been inaccurate information circulating online about how the Pfizer-BioNTech and Oxford-AstraZeneca vaccines work. They both use a type of genetic code called “mRNA” that is different to DNA and so cannot bind with or change it. Not only is it like two mismatching puzzle pieces, but the mRNA also can’t even reach the DNA as DNA is in its own protected section of a cell - the nucleus.  The mRNA works with the cell’s protein-building machinery outside the nucleus to produce the spike protein. 

  • Additionally, mRNA cannot be translated back into DNA. And both mRNA and adenovirus vaccines do not contain the “specialised tools” needed to “copy” or “edit” DNA. 

These vaccines cannot replicate inside the body and only stay in the body for a few days. After helping the cells to produce an immune response against the spike protein, the vaccine is removed by the body. 

The Pfizer-BioNTech and Oxford-AstraZeneca vaccines have a similar safety profile to other vaccines. Side effects that would be expected are mostly “flu-like” symptoms such as a headache, aching, fever, as well as pain and tenderness at the injection site. 

You mention that your GP seems unsure, might there be a specialist that has been involved in your treatment that it would be possible to consult together?  

In terms of Adalimumab specifically, this NHS page suggests that it is not compatible with vaccines that use live viruses. The COVID-19 vaccines that are currently approved in the UK do not use live virus.  

Page 2 of this guidance from the NHS Foundation Trust in Bath in a leaflet around Rheumatology states: “As the vaccine is not a live vaccine, it can be given if you are taking the medications listed above [in the doc linked below, which include Adalimumab]. When taking these medications, it is possible that your response to the vaccine may be dampened. As such, you should continue to follow government guidance on reducing your risk of infection”

Even with this knowledge, we strongly recommend getting to the bottom of this together with your GP/specialist doctor as there might be other considerations which we are not aware of. 

Most side effects of the COVID-19 vaccine are mild and should not last longer than a few days after the vaccine or up to a week afterwards. These include having a sore arm, feeling tired, a headache, feeling achy or feeling or being sick. You can take painkillers such as paracetamol if you need to help with these mild side effects. 

No long-term side effects have been reported among all the thousands of trial participants – if there are any side effects of vaccines, they usually are mild and happen immediately in the first few weeks following the vaccine. There will be continued monitoring of the COVID-19 vaccines now that it is being used in the wider population.  

There is no evidence for this. In a study published in 2018, researchers compared two groups of children. In one group the children had been hospitalised with infections that cannot be vaccinated against (such as many chest infections and stomach upsets). In the other group, none of the children had been hospitalised with these sorts of infections. The researchers then looked at how many vaccines the children in each group had been exposed to and found no significant difference. (If vaccines did weaken the immune system, you would expect to find that the children hospitalised with infections had received more vaccines that the ones who were not hospitalised). 

Pregnancy and fertility

We want to reassure women that there is no evidence to suggest that COVID-19 vaccines will affect fertility. Claims of any effect of COVID-19 vaccination on fertility are speculative and not supported by any data. 

You can find out more about COVID-19 and fertility here.

The original guidance was that pregnant women should not be vaccinated however the UK regulators have updated their guidance to say that pregnant women and those who are breastfeeding can have the vaccine if they are more at risk of getting COVID-19 (such as being a frontline healthcare worker) or have a serious medical condition (for example they were shielding) that puts them at increased risk of being severely unwell with COVID-19. Pregnant women should discuss with a doctor or healthcare professional about whether they should be vaccinated against COVID-19. 

Pregnant women were not included in the COVID-19 vaccine trials however pregnant women have been safely receiving Whooping cough and pertussis vaccines in pregnancy for many years. There is no evidence from laboratory animal studies of the COVID-19 vaccines adverse events or reproductive toxicology effects from the vaccines. 

The Royal College of Obstetricians and Gynecologists have developed a useful leaflet on COVID-19 vaccination in Pregnancy, which you can read here.

There is no reason to believe that the mRNA vaccine technology will have any effect on your ability to become pregnant. 

Although it seems like this technology has been developed very quickly, people have been working on it for decades. From all of this earlier work, we know where the mRNA vaccines go in the body: they mainly stay at the site of injection or go to immune organs such as the lymph nodes and spleen (which is the aim!) and to a lesser extent the liver. The first human trials of mRNA vaccines began in 2006, so the very first people to receive these kinds of vaccines have been living their lives for 15 years now. 

Talking specifically about the Pfizer and Moderna COVID-19 vaccines, we have two kinds of evidence that they will not harm fertility.  

First, in order for the vaccines to be approved, developers have to do "developmental and reproductive toxicity studies" in animals. The two mRNA vaccines that have been approved (Pfizer and Moderna) looked at rats. They gave female rats the vaccine, either before they were allowed to mate, or when they were pregnant. In all of these cases, the rats were able to become pregnant as normal, had normal pregnancies and healthy babies. 

Second, even though pregnant people were excluded from the trials and participants were asked to avoid becoming pregnant, some people did become pregnant by accident. In the Pfizer trial, a total of 23 people became pregnant across both the vaccinated and non-vaccinated group, and one miscarriage occurred in the non-vaccinated group. In the Moderna trial, 6 people became pregnant in the vaccinated group, and 7 in the non-vaccinated group, with one miscarriage in the non-vaccinated group. 

This tells us that the vaccines do not stop people becoming pregnant or cause an increased risk of miscarriage if people do become pregnant. 

Our NHS colleagues recommend that pregnant women speak to their doctor about receiving the vaccine.  

The Royal College of Obstetricians and Gynecologists have recently released this update based on the available evidence.

If helpful, they have also developed a useful leaflet on Covid-19 vaccination in pregnancy, which you might be interested in.

Of the women that became pregnant after participating in Pfizer's mRNA vaccine clinical trial, no poor pregnancy outcomes were reported in the cohort that received the vaccine. 

After vaccination

The ideal timeframe is the interval that was used in the clinical trials, as we know that it works well. The policy at the moment is to deliver the second dose within 12 weeks, longer than the clinical trial interval. This is because the NHS is following Government's expert advisers which say that prioritising a first dose for as many people as possible will save more lives.  

This is because even with just one dose, the Pfizer/BioNTech vaccine has been estimated to offer 89% effectiveness from two weeks after it is given, and the Oxford/AstraZeneca has been estimated to offer 74% effectiveness from two weeks after it is given. 

As the Deputy Chief Medical Officer, Jonathan Van Tam, has said: “The evidence clearly shows vaccinated individuals get almost complete protection after the first dose. Simply put, every time we vaccinate someone a second time, we are not vaccinating someone else for the first time. It means we are missing an opportunity to greatly reduce the chances of the most vulnerable people getting severely ill from COVID-19. If a family has two elderly grandparents and there are two vaccines available, it is better to give both 89 per cent than to give one 95 per cent protection with two quick doses, and the other grandparent no protection at all.” 

When the numbers of people suffering in hospital is much lower, we would expect the interval to return to that indicated by the clinical trial.

People who have been vaccinated are advised to follow the current advice on testing and self-isolation if they develop any coronavirus symptoms or undergo regular testing as a health or social care worker. Vaccination will not affect testing. The lateral flow device (LFD) test detects a different protein of the virus than the one encoded in the vaccine, and the PCR test detects different genes of the virus than the one included in the vaccine.  

The COVID-19 vaccines trial results show that getting vaccinated will reduce your chance of becoming seriously ill and needing to be admitted to hospital with COVID-19 infection. The vaccine cannot give you COVID-19 infection. It is unknown at the moment if there is a chance you might still get or spread COVID-19 even if you have been vaccinated. This means it is important to continue to follow social distancing guidance where you work and in your day-to-day activities. 

Many people are now taking SARS-CoV-2 antibody tests, but a positive antibody test does not necessarily mean a person is protected against COVID-19. This is because there are many distinct antibodies and many different types of test. We do not yet know for certain what kind of antibody shows you have protection against disease, or how much is needed in the blood. 

We receive many emails from people who have received one of the authorised vaccines in the UK, but then take an antibody test that shows they do not have antibodies against the virus.  

They are worried this means the vaccine has not worked – but this is not necessarily the case. Although an antibody test may be able to tell if you have been previously infected with SARS-CoV-2, it will not be able to tell if you are protected following a vaccine. 

Many antibody tests detect an antibody for a type of protein in the SARS-CoV-2 virus called the N-protein. This protein is not found in most COVID-19 vaccines. So even after having a COVID-19 vaccine, in most cases there will not be an antibody response against the N protein, and an antibody test will be negative. 

Pfizer vaccine – 95% efficacy. (that means that in the trial they found a 95% reduction in new cases of the disease in the vaccine group compared with the placebo group). 

JCVI when reviewing the trial data think that the Pfizer vaccine offers good protection a few (2-3 weeks) after the 1st dose. AstraZeneca vaccine prevents around 70% cases (70% efficacy in the trial) and again JCVI think that after a few weeks after the first dose a similar level of protection is received. However, you still need the second booster dose. 

Evidence from the vaccine trials suggests that 21 days after you have had your first dose of vaccine you are likely to have produced an immune response to the vaccine. The COVID-19 vaccine has been found in trials to protect against COVID-19 and that it reduces your chance of becoming seriously ill with COVID-19. It has been approved by the UK regulator MHRA to be safe and effective. The bodies in the UK who review vaccine data (JCVI) and advise the government have reviewed the vaccine trial data and decided that in order to vaccinate the greatest number of people in the shortest possible time that the time between the first and second dose can be lengthened to up to 12 weeks. However, it is still really important that you get the second dose if you are offered it. 

People who have been vaccinated are advised to follow the current advice on testing and self-isolation if they develop any coronavirus symptoms or undergo regular testing as a health or social care worker. Vaccination will not affect testing. The lateral flow device (LFD) test detects a different protein of the virus than the one encoded in the vaccine, and the PCR test detects different genes of the virus than the one included in the vaccine. 

All trial participants are being followed up as is standard. Vaccine effectiveness against symptomatic disease and other outcomes will continue to be monitored regularly as the programme is rolled out and beyond with an increasing follow-up period after vaccination of the initial cohorts. Analyses will be stratified into 3-month follow-up periods for the first year, 6-month periods for the following year and annually thereafter, subject to the number of cases being sufficiently high for an adequately powered analysis. Splines will also be used to model VE by time since vaccination. This will provide early warning of any waning of effectiveness and the need for booster doses.  Then the effectiveness of the vaccine is being monitored by PHE including looking at the following: 

PHE will be monitoring the effectiveness of COVID-19 vaccines against the following outcomes:  

• virologically confirmed symptomatic disease using PCR  

• hospitalisation  

• mortality  

• laboratory confirmed infection (symptomatic or asymptomatic) using PCR or by demonstrating seroconversion due to disease  

• markers of infectiousness and transmissibility - viral load (CT value) and culturable virus  

• onwards person to person transmission 

As with flu, where a new shot is given each year to account for any changes in circulating flu viruses, something similar could happen for coronavirus. 

The Pfizer/BioNTech vaccine has been estimated to offer 89% effectiveness from two weeks after it is given, and the Oxford/AstraZeneca has been estimated to offer 74% effectiveness from two weeks after it is given.  

The fullest protection kicks in around a week or two after the second dose (which is why it’s important for everyone to have their second dose). You may for example have a much better outcome after COVID-19 infection, but it is also thought to increase the duration of the response. These observations will be confirmed within the next few months as the vaccines are rolled out to everyone. 

We expect these vaccines to work for at least a year – if not longer. This will be constantly monitored.