• Preg-CoV Study compares different doses of approved booster vaccines in pregnant women
  • It will provide robust data that could shape national and international guidelines
  • Participants are closely monitored and will have a 24-hour phone line to their study team

An ongoing national COVID-19 vaccine study is urging more pregnant women across south London to step forward, join hundreds of other volunteers and help researchers discover the most effective use of booster vaccines during pregnancy.

The Preg-CoV study is running here at St George’s University Hospitals NHS Foundation Trust and Guy’s as well as St Thomas’ NHS Foundation Trust NHS Trust. It currently has around 300 pregnant women taking part nationally and aims to determine the best vaccine schedules and doses to protect women and their babies against COVID-19.

Gursharon, 36, from Merton, south-west London, is taking part in the National Institute for Health and Care Research (NIHR) Preg-CoV study at St George’s University Hospitals NHS Foundation Trust. The study is being supported by the NIHR Clinical Research Network South London.

The 36-year-old had three miscarriages before giving birth to her daughter, Amira, in April of this year at St George’s Hospital. Gursharon said research has given her everything she wanted from life. She said:

“I’ve wanted to be a mum for such a long time. This pregnancy was so important because my husband, Dennis, and I both really wanted to have a baby. I love being a parent, it is hard work, but everything is worth it to have Amira. I’ve had a few miscarriages and an ectopic pregnancy, which was a devastating experience for my family and I.

“I got vaccinated against COVID-19 to protect Amira, myself and my loved ones from this awful virus. I am an Indian woman, who is asthmatic, so my risk of being seriously ill from COVID-19 was high. I got sick with COVID-19 towards the end of my pregnancy. Thankfully, my symptoms were mild, but it could have been ten times worse if I hadn’t got vaccinated.

“I’m passionate about research, and I want to do my bit to help others. I want to thank the staff at St George’s Hospital for the wonderful care they provided to me, my baby and my family. Volunteering for the Preg-CoV study is the first time I’ve taken part in research, and I will sign up for something similar in the future.”

Gursharon was already vaccinated against COVID-19 before volunteering for the Preg-CoV study.

She had to complete a health questionnaire, have blood taken from her and Amira and have follow-up appointments with a midwife.

The study, led by researchers at St George’s, University of London, compares vaccines currently being used for the UK vaccination programme (Pfizer/BioNTech and Moderna) and new vaccines as they are approved for use, such as Novavax.

The NIHR supported study will also provide vital clinical trial data on the immune response to booster vaccination with different doses of vaccines (full dose Pfizer, half dose Pfizer, half dose Moderna) as well as the immune response to different intervals between doses given in pregnancy. Participants may also be eligible to choose to receive their COVID-19 booster dose alongside the routine whooping cough vaccine.

The current UK guidance is that COVID-19 vaccination should be offered to pregnant women at the same time as the rest of the population. COVID-19 vaccines are safe and effective for pregnant women, and there is a clinical consensus that it is the best way to protect pregnant women and their babies from COVID-19.

Data from the UK Health Security Agency (UKHSA) showed that around 59% of pregnant women had received the first dose of the life-saving COVID-19 jab by the time they delivered their babies, and around 50% had received their second dose. However, further pregnancy-specific research will provide more data on the most effective vaccines, the best gap between vaccine doses for pregnant women and the optimal dose of a booster vaccine in pregnancy.

Hundreds more participants are needed to help provide further findings key to protecting more women and shaping future vaccine guidelines —the study launched in August 2021 and will involve around 700 pregnant women across NIHR-supported sites in England. Volunteers will be closely monitored by health professionals throughout their pregnancy and following the birth of their baby.

Chief Investigator and Professor of Paediatric Infectious Diseases at St George’s, University of London, Professor Paul Heath, said:

“More than 300,000 pregnant women have now been vaccinated with COVID-19 vaccines in the UK, the USA and elsewhere, with no major safety concerns reported. But we do not yet know the optimal schedule to use or the optimal booster dose to use for pregnant women and their babies, and this is what we are addressing in this study.

“We are delighted that around 300 pregnant women have joined the study so far, but we need even more pregnant women across the country to participate. Not only will they receive special monitoring and support around their vaccines, but they will help shape future guidelines and protect pregnant women in the future. It is a really worthwhile, helpful thing to do.”

Pregnant women in the study will receive monitoring and additional support through study visits, compared to those who receive their vaccine outside the study. They will also be provided with a 24-hour phone line should they have any questions for the trial team and an electronic diary to record any symptoms. They will also be reimbursed for travel to their study appointments.

Professor Lucy Chappell, Chief Scientific Adviser for the Department of Health and Social Care, NIHR Chief Executive and Professor of Obstetrics at King’s College London, said:

“Nationally, we have been concerned about pregnant women with COVID-19 needing intensive care unit care and hospitalisation. We understand that pregnant women have been hesitant about taking the COVID-19 vaccine. But we would really like to encourage all pregnant women and those considering pregnancy to get vaccinated so that we can see an impact in these numbers coming down.

“We have seen data on effectiveness and safety of vaccination in pregnancy coming from around the world, following up on the hundreds of thousands of pregnant women who have received COVID-19 vaccines.

“The Preg-CoV study team is leading on this research in the UK to help us gather further information so that we can continue to provide the most accurate advice to parents and parents to be.”

The study will collect blood samples from participants, with a cord blood sample taken after delivery for some participants. For all participants, a baby blood sample will be taken between four and 12 weeks of age. Breastmilk samples will also be collected for a sub-group of participants.

Once enrolled, participants who have already received two or three doses of the COVID-19 vaccine in the community will be eligible to receive a third or fourth booster dose in the study. If they are also due their pertussis (whooping cough) vaccine booster, they can have it at the same time if they wish.

All participants and their babies will be followed up until one year after delivery.

The study is seeking low-risk, pregnant women who are carrying a single baby, are aged 18-45 years old and are between 13-36 weeks’ gestation.

If you are interested in the study or know someone who could be eligible, you can find out more by visiting the Preg-CoV study website.


Notes to editors

Interview details

For interviews with Prof. Paul Heath, contact Rachel Wheeley, Head of Communications and Institutional Events, St. George’s University: rwheeley@sgul.ac.uk.

For interviews with local research staff and participant case studies, please contact NIHR Communications Manager Lewis Deakin via lewis.deakin@nihr.ac.uk.

For all other media queries, please contact the NIHR Press Office: pressoffice@nihr.ac.uk or 020 3328 6730.

Notes to Editors

  • The Preg-CoV study is supported by the National Institute for Health and Care Research (NIHR) and backed by £7.5 million of government funding from the UK Vaccines Taskforce.
  • No safety concerns relating to COVID-19 vaccination of pregnant women have been found in published studies to date. The rate of vaccine side-effects appears to be similar in pregnant and non-pregnant populations.
  • The UKHSA publishes figures for vaccine uptake in pregnant women every four weeks in its weekly surveillance reports. The latest figures were published on 12 May 2022.
  • Following 160,000 pregnant women being vaccinated in the US and no safety concerns being raised, the Pfizer/BioNTech and Moderna vaccines were recommended by the independent experts at the Joint Committee on Vaccination and Immunisation (JCVI) for pregnant women in the UK.

Site list

Lead site: St George’s Hospital, London

St. James’s University Hospital, Leeds

Princess Royal Hospital, Telford

Royal Free Hospital, London

Southampton General Hospital

Royal Victoria Hospital, Newcastle

Guy’s and St Thomas’ NHS Foundation Trust, London


Sites taking part in other stages of the Preg-CoV study include:

Birmingham Heartlands Hospital

Liverpool Women’s Hospital

Milton Keynes University Hospital

Royal Cornwall Hospital, Truro

Royal Preston Hospital, Lancashire

St Mary’s Hospital, Manchester

St Michael’s Hospital, Bristol

Epsom and St Helier University Hospitals NHS Trust, London

Hammersmith Hospital, Queens Charlotte’s & Chelsea Hospital, London

About the National Institute for Health and Care Research

The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research. We do this by:

  • Funding high quality, timely research that benefits the NHS, public health and social care;
  • Investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services;
  • Partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research;
  • Attracting, training and supporting the best researchers to tackle complex health and social care challenges;
  • Collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system;
  • Funding applied global health research and training to meet the needs of the poorest people in low and middle income countries.

The NIHR is funded by the Department of Health and Social Care. Its work in low and middle income countries is principally funded through UK Aid from the UK government.

About St George’s, University of London

St George’s, University of London is the UK’s specialist health university. We are shaping modern health with transformative research, expert teaching and hands-on learning.

Our three research institutes focus on biomedical and scientific discovery, advancing the prevention and treatment of disease in the fields of population health, heart disease and infection – three of the greatest challenges to global health in the 21st century.

We provide a world-class multi-professional health sciences education that equips our graduates to meet today’s healthcare needs through relevant scientific research, clinical excellence, strong interpersonal skills and team-based working. Sharing a clinical environment with a major London teaching hospital, our innovative approach to education results in well-rounded, highly skilled clinicians, scientists, and health and social care professionals.

Why pregnant women are still needed for COVID-19 vaccine studies

Ongoing global studies have found that pregnant women are more likely to develop severe COVID-19 disease than non-pregnant women of the same age. Pregnant women who develop COVID-19 symptoms are two to three times more likely to have their baby early. Pregnant women with COVID-19 also have a higher mortality rate than pregnant women without COVID-19. Pregnant women can and should get vaccinated now. It is the best way to protect them and their baby. However, further pregnancy-specific research is needed on COVID-19 vaccines to work out how to optimise that protection.

What is this trial aiming to find out?

The trial assesses vaccines currently being used for the UK vaccination programme, as well as any new vaccines as they are approved. Low-risk pregnant women aged 18-45 years old and between 13 weeks’ and 36 weeks’ gestation can be considered for enrolment onto the study.

Once successfully enrolled, those women who have already received two or three doses in the community will be offered a booster (third or fourth) dose in the study; they will be randomised to receive a full dose of the Pfizer vaccine or a half dose of the Pfizer vaccine or a half dose of the Moderna vaccine. Full dose Pfizer and half dose Moderna vaccines are the standard boosters being given in the routine programme. The half-dose Pfizer has been assessed in another VTF-funded study called COV-BOOST (https://www.covboost.org.uk/home) and has shown similar immune responses and potentially fewer side effects than the full dose Pfizer dose.

If they are also due their pertussis (whooping cough) vaccine booster, they can have it at the same time if they wish.

Blood samples will be taken from participants throughout the study. For some participants, a cord blood sample will be taken after delivery. For all participants, a baby blood sample will be taken between four and 12 weeks of age. For a sub-group of participants, breast milk samples will also be collected. All participants will be followed up to 12 months after delivery. Participants will be asked to complete a symptom diary, and any significant medical events will be investigated.


Results of the trial will be disseminated in peer-reviewed scientific journals, internal reports, conference presentations and online publications.

What’s next?

If you would like to find out more, please read the Study Information Booklet, and if you are interested in taking part, please complete our pre-screening questionnaire.

Compared to non-pregnant women with COVID-19, pregnant women with COVID-19 have higher rates of intensive care unit admission and compared to pregnant women without COVID-19, pregnant women have overall worse maternal outcomes. Approximately two in three pregnant women with COVID-19 will have no symptoms, and those pregnant women who do have symptoms will usually have mild symptoms. However, a small number of pregnant women can become unwell with COVID-19, with the risk of severe illness being greater in the third trimester.

The studies have also found that women from black, Asian and minority ethnic backgrounds are more likely than other women to be admitted to hospital for COVID-19. Other risk factors that increase the chances of pregnant women developing severe COVID-19 disease and requiring hospital admission are being aged 35 years and over, having a body mass index (BMI) of 25 or more and having health conditions such as high blood pressure and diabetes. The risk of developing severe illness with COVID19 in pregnancy has also been shown to be increased in women living in areas or households with increased socioeconomic deprivation.

By performing this trial, we aim to gather further specific data on the safety of COVID-19 vaccines in pregnant women and their babies to add to the already clear data that the vaccine is safe in pregnant women. We will also compare the immune responses to different COVID-19 vaccines, to different doses of booster vaccines and when given other routine vaccines.

What vaccines are being used in this trial?

Currently, the COVID-19 vaccines that are to be studied in this trial are:

o Pfizer/BioNTech BNT162b2 – referred to as Pfizer

o COVID-19 Vaccine Moderna –referred to as Moderna

o Novavax NNVXCoV2373 – referred to as Novavax (will ONLY be used in the trial when it is used in the UK)

o AstraZeneca ChAdOx1 nCOV-19 – referred to as AstraZeneca (will ONLY be used for participants who have received one dose of the vaccine already (pre-trial) and are in Cohort four