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September 02, 2021 @ 07:30 +03:00
Covid-19 vaccines are still “stunningly effective” despite fears that immunity may dwindle over time, experts have said. There have been some concerns about the efficacy of Covid-19 vaccines after a number of recent studies indicated a growing number of so-called “breakthrough” Covid cases among the fully vaccinated. The studies have, however, shown that the fully vaccinated are still highly protected against severe infection, hospitalization and death caused by the virus.
Preliminary data published by the Israeli government in July showed that the Pfizer vaccine was just 16% effective against symptomatic infection for people who had received two doses in January. For people who had been fully vaccinated by April, the vaccine was 79% effective against symptomatic infection, suggesting that immunity gained through immunization depletes over time.
A piece of research funded by Pfizer, published in July, showed that the efficacy of the Pfizer-BioNTech vaccine was strongest between one week and two months after receiving the second dose, coming in at 96.2%. It then, however, declined by an average of 6% every two months. Four to six months after a second dose, its effectiveness fell to around 84%.
An earlier English study, published in May, found that the Pfizer-BioNTech vaccine was 88% effective at preventing symptomatic disease from the delta variant. Against the alpha variant, once the dominant strain in the U.K., the vaccine was 93% effective at preventing symptomatic disease. Meanwhile, the research found that two doses of the Oxford-AstraZeneca vaccine were 60% effective at preventing symptomatic disease from the delta variant, compared to a 66% efficacy rate against the alpha variant.
The data showed the importance of having two doses of these vaccines as the efficacy of both shots against symptomatic infection from the delta variant stood at just 33% three weeks after the first dose, the study found. If the virus continued to mutate, it did not necessarily mean it would become more resistant to existing vaccines however.
Covid vaccines remain ‘stunningly effective,’ even as delta concerns grow, CNBC, Sep 2