A national Covid-19 vaccine trial is now calling for pregnant women from across the South.
The study, taking place at University Hospital Southampton, will start to recruit participants later this month.
It will look into the immune response to vaccination at different dose intervals - either four to six weeks or eight to 12 weeks.
Participants will need to be between 18 and 44-years-old and 13 to 34 weeks pregnant on the day of vaccination.
Women who have had previous vaccinations can still take part as the trial focuses on boosters, the size of the dose and which vaccine works best.
The study, led by St George's, University of London, is backed by Â£7.5 million of government funding.
More than 600 pregnant women will take part in the trial across 13 sites.
Participants will receive two doses of either the Pfizer/BioNTech or the Moderna vaccines - 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.
It will help to show how the vaccine works to protect pregnant mothers and their babies against Covid-19.
The Chancellor and former 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.
"I encourage anyone who is pregnant and eligible to sign-up and contribute to research that will save lives for years to come."
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