Israeli researchers found that protection conferred by Pfizer’s COVID-19 vaccine waned after several months across all age groups against the Delta variant, coming after a UK study revealed that the Delta variant is still highly transmissible among fully vaccinated household members.
In a study published in the New England Journal of Medicine, Yair Goldberg, of the Technion-Israel Institute of Technology in Haifa, found that the rates of infection in July were higher among adults ages 60 and older who got the vaccine in January, as compared with those who got the vaccine in March.
Among adults between the ages of 40 to 59, similar rates of infection were reported, the researchers said. Those who got the shot in February versus those who got it in April saw higher rates of infection, and people aged 16 to 39 who were vaccinated in March versus those vaccinated in May experienced a similar trend, the authors wrote.
They concluded that protection conferred against the COVID-19 Delta variant “waned in all age groups” just months after getting the second dose.
For the adult age group, there were 0.34 severe COVID-19 cases per 1,000 for those aged 60 and older who were vaccinated in January, and 0.12 cases of severe infection per 1,000 for those vaccinated in April and May, according to the authors of the study.
The Israeli team cautioned about the possibility of preexisting conditions that could not be factored into their study.
After their findings, the researchers then argued because the Pfizer vaccine’s efficacy drops after a few months, it’s needed to promote booster shots.
“The results presented here provided an epidemiologic basis for the decision by the Israeli Ministry of Health on July 30, 2021, to approve the administration of a booster (third dose) of COVID-19 vaccine to persons who had been vaccinated at least 5 months previously,” the team concluded. “The findings also suggest the need to follow the effects of waning immunity closely and to inform policymakers worldwide who are facing decisions regarding the administration of booster vaccinations.”
