In a new study from King’s College London and elsewhere, researchers found the protection from two doses of the Pfizer and AstraZeneca vaccines fades within less than six months.
The finding suggests that booster shots may be needed to ensure prolonged coverage. The result comes as several countries are rolling out additional jabs for the fully vaccinated.
The team found the Pfizer jab was 88% effective a month after the second dose, but protection fell to 74% after five to six months.
They used real-world data gathered via a mobile phone app with over a million active users, who log details on their vaccinations and test results. The team analyzed more than 1.2 million test results.
They found the protection from the AstraZeneca vaccine fell from 77% one month after a second dose to 67% after four to five months.
The team says that more data was needed on how vaccine effectiveness changes in different age groups.
They warn that waning vaccine effectiveness among the most vulnerable could lead to more hospitalizations and deaths by winter.
If high levels of infection remain, fuelled by the more transmissible Delta variant and easing of restrictions, this scenario could mean increased hospitalizations and deaths.
Other recent studies have found that the effectiveness of the Pfizer vaccine declines faster than that of AstraZeneca.
If you care about COVID vaccines, please read studies about this single-shot COVID-19 vaccine can protect against variants and findings of Pfizer vaccine may protect against COVID variants in these people.
For more information about COVID vaccines and your health, please see recent studies about this new COVID-19 vaccine can give the body ‘border protection’ and results showing that COVID-19 mRNA vaccines less effective for Delta variant.
One researcher of the study is Professor Tim Spector.
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