Pfizer/BioNTech Fourth COVID-19 Vaccine Dose Protects Against Omicron For At Least One Month

A fourth dose of the COVID-19 vaccine from Pfizer Inc PFE and BioNTech SE BNTX provided significant protection against severe disease, hospitalization, and death for at least a month in older individuals. The study was conducted in Israel, when the Omicron variant was dominant.

The estimated effectiveness of the fourth dose during days 7 to 30 after administration was 45% against infection, 55% for symptomatic disease, 68% for hospitalization, 62% for severe illness, and 74% for death compared with a third dose given at least fourth months earlier.

The study compared 182,122 individuals aged 60 and older who received a fourth dose and 182,122 very similar people who had received a third dose but not a fourth.

"The results of our real-world study suggest that a fourth vaccine dose is, at least initially, effective against the Omicron variant," the researchers said. "Additional follow-up will allow further assessment of the protection provided by the fourth dose over time." 

A recently published Israeli study that looked only at breakthrough infections and serious illness rates after the fourth dose found that efficacy declined quickly versus disease but remained steady versus severe illness.

Price Action: PFE shares are down 2.43% at $51.83, and BNTX stock is down 8.89% at $159.71 during the market session on the last check Monday.