Credit CDC
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While we don't have as much safety data on mRNA vaccines in pregnant women and their offspring as we have on other cohorts, so far we've seen no safety signals of note, and the risks from COVID infection are well known (see Preprint: Impact of SARS-CoV-2 Variant on the Severity of Maternal Infection and Perinatal Outcomes).
The CDC, and the UK's PHE, both recommend pregnant women consider getting vaccinated, with the CDC stating:
Pregnant and Recently Pregnant People Are at Increased Risk for Severe Illness from COVID-19
Although the overall risk of severe illness is low, pregnant and recently pregnant people are at an increased risk for severe illness from COVID-19 when compared with non-pregnant people. Severe illness includes illness that requires hospitalization, intensive care, or a ventilator or special equipment to breathe, or illness that results in death. Additionally, pregnant people with COVID-19 are at increased risk of preterm birth and might be at increased risk of other adverse pregnancy outcomes compared with pregnant women without COVID-19.
If you are facing a decision about whether to receive a COVID-19 vaccine while pregnant, consider:
- Your risk of exposure to COVID-19
- The risks of severe illness
- The known benefits of vaccination
- The limited but growing evidence about the safety of vaccinations during pregnancy
Limited Data Are Available about the Safety of COVID-19 Vaccines for People Who Are PregnantBased on how these vaccines work in the body, experts believe they are unlikely to pose a risk for people who are pregnant. However, there are currently limited data on the safety of COVID-19 vaccines in pregnant people.
- Clinical trials that study the safety of COVID-19 vaccines and how well they work in pregnant people are underway or planned. Vaccine manufacturers are also collecting and reviewing data from people in the completed clinical trials who received vaccine and became pregnant.
- Studies in animals receiving a Moderna, Pfizer-BioNTech, or J&J/Janssen COVID-19 vaccine before or during pregnancy found no safety concerns in pregnant animals or their babies.
While the news thus far is reassuring, limited safety data on the vaccine in pregnant women undoubtedly leads to a degree of vaccine hesitancy, and a lower uptake among pregnant women.
The risks of not being vaccinated during this pandemic are real, however. The CDC maintains a Data on COVID-19 during Pregnancy website, and while they caution that their data is far from complete, they list 17,555 hospitalized cases, and 119 deaths.
Additional studies, on the safety and effectiveness of COVID vaccines in pregnant women are ongoing, or are planned. Today the UK has launched a new study (Preg-CoV) that will help determine the best vaccine dosing interval for pregnant women.
Although the manufacturer's recommendations for dosing are for a 3 to 4 week interval between the 1st and 2nd dose, the UK - faced with a limited supply last winter - opted for an 8 to 12 week interval in order to get as many 1st jabs into the arms of the public as possible.
In recent months it has become apparent that 1 dose of the vaccine isn't nearly as protective against the Delta variant as it was against Alpha, raising doubts over that strategy.
But at the same time, we've seen some studies (see UK Preprint: PITCH study – Antibody & Cellular Immune Responses after Two Different Dosing Schedules of the Pfizer Vaccine) suggesting the longer dosing schedule may provide more durable protection.
We've also seen data from Israel, which began vaccinating in late 2020 using the 3-4 week dosing schedule, suggesting that vaccine effectiveness begins to wane within a few months (see Israeli, UK data offer mixed signals on vaccine’s potency against Delta strain).
While plausible - unless and until we see similar declines in vaccine effectiveness in other countries vaccinating on a 3-4 week interval - the Israeli data remains an outlier.
In hopes of determining the best dosing interval - at least among pregnant women - the UK is looking for hundreds of volunteers to take part in the Preg-CoV study.
New study into COVID-19 vaccine dose interval for pregnant women
Extensive real-world data shows vaccines are safe and highly effective for pregnant women.Published 3 August 2021
- New government-funded clinical trial investigating best coronavirus (COVID-19) vaccine dose interval for pregnant women launched in England
The country’s largest clinical trial investigating the best gap between first and second COVID-19 vaccine doses for pregnant women is being launched in England today (Tuesday 3 August).
- Research shows pregnant women more likely to become seriously ill from COVID-19 and 98% of those in hospital due to COVID-19 are unvaccinated
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 3 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 and led by St George’s, University of London, will provide vital clinical trial data on the immune response to vaccination at different dose intervals – either 4 to 6 weeks or 8 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.
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 2 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.
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 2 doses of a COVID-19 vaccine – or one dose if they’ve already had their first – at either the shorter interval of 4 to 6 weeks, or the longer interval of 8 to 12 weeks.
They will be scheduled to attend 9 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.
