Covid Protection Wanes Months After Second Shot, Studies Show

Immunity provided by the Covid-19 vaccine from partners Pfizer Inc. and BioNTech SE weakens significantly within months, with men having less protection than women, according to research that supports the use of booster doses.

Protective antibodies decreased continuously during the six months after the administration of the second dose of the vaccine, according to a study of about 5,000 Israeli health workers, published Wednesday in the New England Journal of Medicine. The levels fell first at a sharp pace and later at a more moderate one.

Researchers worldwide are trying to identify the critical threshold of antibodies needed to ...