Fourth doses of the COVID-19 vaccine don't appear to offer significant protection against catching omicron according to a preliminary study conducted in Israel, the first country to authorize a [first and] second booster for its general population.
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These findings appear to confirm doubts expressed by the European Union's top drug regulator last week. Marco Cavaleri, the European Medicines Agency's head of vaccines strategy, said at a news briefing there's no data supporting the broad effectiveness of fourth boosters.
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Researchers say that although it's true that there's no clinical data proving the effectiveness of multiple boosters, there's also no science to back up the idea that frequent boosters could cause "fatigue" in the population. That's because the research has never been attempted.
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While T cell [B-cell?]exhaustion can be observed in cancer or HIV patients in response to some immune-based treatments, it's never been observed in humans in response to frequent COVID-19 vaccination. Obst said that although there's little clinical data behind it, Cavaleri's concern makes sense.
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The COVID-19 vaccines have been held to an impossible standard, he said. When the phase three studies on the quality of the Moderna and Pfizer vaccines were presented in the US in December 2020, they showed claimed a 95% efficacy against mild [COVID-19] illness.