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New study into Covid-19 vaccine dose interval for pregnant women launches

Published: 03 August 2021


The country’s largest clinical trial investigating the best gap between first and second Covid-19 vaccine doses for pregnant women, led by St George’s, University of London, is being launched in England today – extending the university’s broad portfolio of Covid-19 research.

Following 130,000 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. Almost 52,000 pregnant women in England have now been vaccinated - similarly, with no safety concerns reported.

Data published last week by NHS England and the University of Oxford also shows no pregnant women who have had both doses of a vaccine have been admitted to hospital with Covid-19. Only three have been admitted after having their first dose, meaning 98% of those admitted to hospital have not received a jab. 

The Preg-CoV study, backed by £7.5 million of government funding, will provide vital clinical trial data on the immune response to vaccination at different dose intervals - either four to six weeks or eight to 12 weeks. 

This data will help determine the best dosage interval and tell us more about how the vaccine works to protect pregnant mothers and their babies against Covid-19.

Chief Investigator of the trial and Professor of Paediatric Infectious Diseases at St George's, University of London, Professor Paul Heath, said, “Tens of thousands of pregnant women have now been vaccinated in both the US and the UK with no safety concerns reported, but we still lack robust, prospective clinical trial data on Covid-19 vaccines in pregnant women. This includes the best schedule to use to maximally protect them against Covid-19.

“We are extremely pleased to commence the Preg-CoV trial, which aims to fill these gaps in our knowledge and will ultimately inform policy recommendations on the optimal use of Covid-19 vaccines in pregnancy.”

Vaccines have been given to pregnant women to protect them and their babies from diseases for years - including for whooping cough and flu.

The trial will involve over 600 pregnant women being vaccinated with either the Pfizer/BioNTech or the Moderna vaccine. They will be closely monitored by health professionals throughout their pregnancy and following the birth, with the safety of the women taking part in the trial the utmost priority. 

The Preg-CoV participants will need to be between 18 and 44 years old, have no health conditions and be between 13 and 34 weeks pregnant on the day of vaccination. They will receive two doses of a Covid-19 vaccine - or one dose if they’ve already had their first - at either the shorter interval of four to six weeks, or the longer interval of eight to 12 weeks.

They will be scheduled to attend nine visits in total and will be required to complete an electronic diary between visits on any symptoms. They will also be given a 24-hour mobile number so they can contact one of the trial team at any time if they have concerns.

The scientists behind the trial will analyse blood samples from the participants and one blood sample from their newborn babies, alongside samples from breastmilk. They will use the samples to help understand more about how the vaccines are protecting these individuals from Covid-19, with initial results expected by the end of the year.

The study will open for applications from volunteers today via the study’s website, with vaccinations set to start from mid-August. Participants will also be recruited to the study by invites sent through the NHS Covid-19 Vaccine Research Registry, which allows research teams to speak to suitable volunteers who have signed up to be contacted about taking part in vaccine studies.

Professor Asma Khalil, lead obstetrician for the trial and Professor of Obstetrics and Maternal Fetal Medicine at St George’s, University of London and St George’s Hospital, said: "It's important to highlight that all participants in this study will receive a Covid-19 vaccine. This is particularly important with the rising number of cases, the easing of restrictions and low vaccine uptake among pregnant women.

"We know that only around one in three pregnant women giving birth at our hospital have been vaccinated, so the more that can be done to encourage uptake, the better."

Minister for Covid-19 Vaccine Deployment, Nadhim Zahawi, said, “Pregnant women are more likely to get seriously ill from Covid-19 and we know that vaccines are safe for them and make a huge difference – in fact no pregnant woman with two jabs has required hospitalisation with Covid-19.

“This government-backed trial will provide more data about how we can best protect pregnant women and their babies, and we can use this evidence to inform future vaccination programmes.

“I encourage anyone who is pregnant and eligible to sign-up and contribute to research that will save lives for years to come.”

The trial will be run across 13 National Institute for Health Research (NIHR) sites in England - including in London, Liverpool and Leeds. All the trial sites are working on ways of including participants from a wide variety of backgrounds and individuals from ethnic minorities are encouraged to apply.

This study represents a broad portfolio of Covid-19 research at St George’s, University of London, including involvement in multiple vaccine studies. If you are interested in volunteering for the trial, applications can be submitted on the study website.

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