Two studies published in the New England Journal of Medicine show that the immune protection from Pfizer's COVID-19 vaccine begins to wane after two months. The first study from Israel found that antibody levels decreased, "especially among men, among persons 65 years of age or older, and among persons with immunosuppression."
The study provides more evidence as to why a booster shot may be necessary, especially in older adults.
"Published work about many vaccines, such as those against measles, mumps, and rubella, has shown a small decrease each year of 5 to 10% in the neutralizing antibody levels," the study authors wrote. "We found that a significant and rapid decrease in humoral response to the BNT162b2 vaccine was observed within months after vaccination."
A second study from Qatar found that antibody levels rise rapidly after the first dose and then peak one month after the second dose is administered.
"BNT162b2-induced protection against infection builds rapidly after the first dose, peaks in the first month after the second dose, and then gradually wanes in subsequent months," Laith Abu-Raddad of Weill Cornell Medicine-Qatar and colleagues wrote. "The waning appears to accelerate after the fourth month, to reach a low level of approximately 20% in subsequent months," they added.
Despite the waning antibody levels, Pfizer's vaccine continues to provide strong protection against severe cases of COVID, hospitalizations, and death. The vaccine is still 90% effective and protects against all coronavirus variants of concern, including the delta variant.