AstraZeneca Booster Shot Needed to Shore Up Protection, Study Finds

(Bloomberg) -- Protection from severe illness following two shots of AstraZeneca Plc’s Covid-19 vaccine starts declining about three months after the second dose, according to a study that reinforces the need for boosters. 

The researchers analyzed data for 2 million people in Scotland and 42 million people in Brazil and assessed the risk of severe Covid outcomes, including hospitalizations and deaths, three months after the second dose. They didn’t analyze Astra’s shot against the fast-spreading omicron variant, which wasn’t circulating at the time. 

“We found waning vaccine protection against Covid-19 hospital admissions and deaths both in Scotland and Brazil,” researchers said in the study, published in The Lancet on Monday. They said consideration should be given to providing booster vaccine doses for people who have received a primary course of Astra’s shot, which was developed with the University of Oxford. 

Britain, which relied on the Astra vaccine for primary inoculation of over 40s, is already engaged in a rapid rollout of booster mRNA shots from either Pfizer Inc. and partner BioNTech SE or Moderna Inc. Prime Minister Boris Johnson is hoping that bolstering the population’s immunity could help curb the spread of omicron and relieve building pressure on the country’s National Health Service. 

A growing body of evidence suggests that three courses of the world’s most widely-used Covid vaccines will be needed to generate enough antibodies against omicron. Antibodies are only one part of a person’s immune defense, however, with T-cells also playing a role, making it difficult to assess how effective the current generation of vaccines is against omicron. 

Astra Chief Executive Officer Pascal Soriot said last month that the company’s vaccine could be the reason the U.K. was faring better with Covid hospitalizations than Europe at the time. He suggested the slower-developing T-cell response might mean the shot was providing more durable immunity in the aged, though said more data was needed -- a view echoed by scientists.

Penny Ward, a professor in pharmaceutical medicine at King’s College London, said that while the paper gives a “rather alarming impression at first glance,” it also shows that there is “sustained vaccine effectiveness in preventing hospitalization and death from Covid of at least 50% across the period of the study.” 

She added the data reiterate the importance for people to “get out and get boosted as fast as possible.” 

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