An Israeli study found that antibody levels after a fourth dose of the Pfizer BioNTech COVID-19 vaccine returned to similar levels as after the 3rd dose after about four months.
The study, conducted among health care workers at the Sheba Medical Center, the largest hospital in Israel, found that the immunological protection of the 4th dose “was much smaller and had waned completely by 13 weeks after vaccination.”
It found “no substantial additional effectiveness over a third dose at 15 to 26 weeks after vaccination.”
The authors concluded that these findings suggest the 4th dose and possible future boosters “should be timed wisely to coincide with disease waves or to be available seasonally, similar to the influenza vaccine.”
The six-month follow-up study was published in The New England Journal of Medicine on Nov. 9.
The study led by Dr. Michal Canetti and Dr. Gili Regev-Yochay, the head of the Infection Prevention and Control unit at Sheba, followed employees who did not fall ill before the study, beginning Dec. 27, 2021, to July 10, 2022, when the Omicron virus variant was dominant in Israel.
The researchers tested the immune response of 6,113 employees and performed a monthly follow-up of the antibody levels in their blood. In addition, they performed a vaccine effectiveness analysis of 11,176 employees after the 2nd, 3rd, and 4th doses.
The weekly levels of antibodies throughout the period after the receipt of the 3rd and 4th doses were found to be similar and the study said were higher than after receiving the 2nd dose.
Effectiveness of the fourth dose against infection started at just 52 percent during the first five weeks after administration and dropped to negative 2 percent at 15 to 26 weeks. A growing number of studies have detected negative effectiveness, which means the vaccinated are more likely to get infected.
Pfizer did not respond to a request for comment.
Limitations of the paper included the cohort only consisting of health care workers.
‘Reassessment of Future Booster Campaigns’
An Israeli study published in Nature Communications on Nov. 7 found that the short-lived immunity and rapid waning of the Pfizer BioNTech COVID-19 vaccine necessitate the reevaluation of future COVID-19 vaccination campaigns.
The authors of that study said that “its relatively small effect on transmissibility of Omicron … and its rapid waning call for reassessment of future booster campaigns.”
The authors said the results indicated that the vaccines “may focus the need for boosters for high-risk groups only,” and they added that if the lack of sterilizing immunity proves consistent, it “may have major ramifications on global pandemic preparedness” and vaccination rollout.