The protection offered by two doses of the Oxford/AstraZeneca vaccine, including against severe disease, begins to wane after three months, according to a new study showing the importance of booster programmes. from the second injection.
The researchers analyzed data on 2 million people in Scotland and 42 million people in Brazil who received two doses of the vaccine. Their findings were published in a New articles reviewed at The Lancet late on Monday. Omicron variants were not circulating during the study.
“We are seeing a weakening of vaccine protection [the vaccine] against Covid-19 hospitalizations and deaths in both Scotland and Brazil, which became apparent within three months of the second dose of the vaccine,” they wrote. “It is necessary to consider providing booster doses of vaccine to those already vaccinated [the vaccine]. ”
The researchers were able to compare the Scottish and Brazilian data because a similar interval of three months was used between doses and because those most at risk of severe illness and healthcare workers were given priority to get the injections. strains in both places.
During the study, variants of the virus – Delta in Scotland, Gamma in Brazil – were circulating that, when the vaccine’s protection was waning, “likely” contributed to the reduced effectiveness.
The UK, where many received the AstraZeneca vaccine earlier this year, has moved to give all adults an mRNA booster shot to fight the rapidly spreading variant of Omicron.
Other wealthy nations have ramped up their ramp-up programs to limit the spread of the virus. Preliminary, early evidence suggests that a two-shot course of the widely used vaccine produces a smaller amount of antibodies against Omicron than previous variants, but it is unclear how this translates to how is the effect.
The head of the European Medicines Agency said that it will take some time to reach a consensus on whether footage targeting Omicron would become necessary, the Financial Times reported on Monday.
Scientists had hoped that the two shots would still provide protection from severe illness, because immunity is not just a function of antibody numbers. However, some experts not involved in the study expressed concern that this could change that perception.
Peter English, a retired consultant in infectious disease control, says the prevailing assumption so far is protection against serious illness and more serious outcomes, such as T cells. , will last, “perhaps for many years”.
“This article casts doubt on these assumptions,” he said. “It shows that protection against severe disease declines over time, with the likelihood of severe illness becoming about five times higher, compared with immediately after vaccination, after just a few months.”
“This is very concerning,” he said. “In the short term, it highlights the need for an additional dose, and in the medium and long term, it raises the question of how effectively the current generation of vaccines can prevent future disease. any.”
Another outside expert, Penny Ward, a visiting professor of pharmacy at King’s College London, said there was still “sustained effectiveness of vaccines” in preventing at least 50% of hospitalizations and deaths. died from Covid during the follow-up period. But she agrees that a booster shot is needed to provide a high level of protection.
Aziz Sheikh, an author of the study and head of the University of Edinburgh’s Usher Institute, says that by determining when impairment begins to occur in people who have been vaccinated with AstraZeneca, “the government can can design enhancement programs that can ensure maximum protection is maintained”.
“If you qualify for a boost and you haven’t already, I highly recommend you book one early,” he said.
Pascal Soriot, CEO of AstraZeneca, there was last month suggests that using vaccines in older people may help prevent severe illness in older adults for longer. However, he said there was no evidence and more data was needed.
Oxford and AstraZeneca did not respond to requests for comment.
