Just like the first, second and third COVID-19 vaccine doses that came before it, the “protection” of a fourth Pfizer/BioNTech (BNT162b2) vaccine dose waned completely within four months returning to similar levels seen after the third vaccine dose.
According to a prospective cohort study published on Nov. 9 in The New England Journal of Medicine the immunological protection of a fourth COVID-19 vaccine dose “was much smaller and had waned completely by 13 weeks after vaccination.” Researchers also found “no substantial additional effectiveness over a third dose at 15 to 26 weeks after vaccination.”
The study, led by Dr. Michal Canetti and Dr. Gili Regev-Yochay, was conducted among healthcare workers at the Sheba Medical Center — the largest hospital in Israel. Researchers followed 6,113 employees who did not get COVID-19 before the study beginning Dec. 27, 2021, to July 10, 2022, and performed a vaccine effectiveness analysis of 11,176 employees after receiving their second, third and fourth doses. Researchers then performed a monthly follow-up of the antibody levels in their blood.
Results showed the effectiveness of a fourth COVID-19 vaccine dose against infection started at only 52% during the first five weeks following administration and dropped to negative 2% at 15 to 26 weeks. A growing number of studies have detected negative effectiveness, which means the vaccinated are more likely to get infected after receiving a vaccine.
The authors concluded the “additional immunologic advantage” of the fourth dose was much smaller and had waned completely by 13 weeks after vaccination.
“This finding correlated with waning vaccine effectiveness among recipients of a fourth dose, which culminated in no substantial additional effectiveness over a third dose at 15 to 26 weeks after vaccination,” they added.
The authors said their findings suggest a fourth dose and future boosters “should be timed wisely to coincide with disease waves or to be available seasonally, similar to the influenza vaccine.”