A third shot of the vaccine lifted immune response in volunteers who had already received two. …
A third dose of the Covid-19 vaccine developed by AstraZeneca and the University of Oxford generated a strong immune response in clinical trial volunteers, Oxford researchers reported on Monday.
The finding indicates that the AstraZeneca vaccine could be an option should third shots end up being needed, for example, to extend immunity. To date, the vaccine has been given as two doses, typically between four and 12 weeks apart.
The new data, detailed in a preprint manuscript that has not yet been peer reviewed, came from 90 study volunteers in Britain who were among the earliest to receive the shots in a clinical trial last year. This past March, they were given a third dose, roughly 30 weeks after their second.
Laboratory analyses showed that the third dose increased levels of antibodies to the virus in the volunteers to a point higher than seen a month after their second dose — an encouraging sign that the third shot would be likely to bring greater protection if the effectiveness of two doses waned over time.
“We do have to be in a position where we could boost if it turned out that was necessary,” Prof. Andrew Pollard, an Oxford researcher who has led studies of the vaccine, said in a news conference on Monday. “I think we have encouraging data in this preprint to show that boosters could be used and would be effective at boosting the immune response.”
Scientists and policymakers do not yet know whether booster shots may be needed.
Scientists reported Monday that the vaccines made by Pfizer-BioNTech and Moderna set off a persistent immune reaction in the body that may protect against the coronavirus for years, but
