"We report SARS-CoV-2 vaccine effectiveness against infection (VE-I) and death (VE-D) by vaccine type (n = 780,225) in the Veterans Health Administration, covering 2.7% of the U.S. population.
From February to October 2021, VE-I declined from 87.9% to 48.1%,
and the decline was greatest for the Janssen vaccine resulting in a VE-I of 13.1%.
Although breakthrough infection increased risk of death, vaccination remained protective against death in persons who became infected during the Delta surge.
From July to October 2021, VE-D for age 65 years was 73.0% for Janssen, 81.5% for Moderna, and 84.3% for Pfizer-BioNTech;
VE-D for age ≥65 years was 52.2% for Janssen, 75.5% for Moderna, and 70.1% for Pfizer-BioNTech.
Findings support continued efforts to increase vaccination, booster campaigns, and multiple, additional layers of protection against infection.
The messenger RNA vaccines BNT162b2 (Pfizer–BioNTech) and mRNA-1273 (Moderna) and the viral vector vaccine JNJ-78436735 (Janssen) have effectively prevented clinically significant disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) since their rollout in the U.S. in late 2020
Vaccines have also reduced the incidence of asymptomatic infection and associated infectivity
However, by July 2021, the U.S. experienced a surge in cases of COVID-19, dominated by the B.1.617.2 (Delta) variant
... three reports of the U.S. Centers for Disease Control (CDC) in August 2021 demonstrated protection against infection had declined in mid-summer as the Delta variant rose to dominance; protection against hospitalization and death remained high
Breakthrough infections, illness, hospitalizations, and deaths have since continued to emerge in vaccine recipients.
This phenomenon has been most comprehensively monitored in Israel, where high levels of transmission of the Delta variant led to a resurgent outbreak in mid-June 2021 despite a successful nationwide campaign to vaccinate the population
Israel authorized boosters of the Pfizer-BioNTech vaccine for adults age ≥ 60 years in July 2021 and extended this authorization to adults age ≥ 50 years in August 2021.
Rates of infection and severe illness subsequently declined in those who received a booster.
Based largely on these data, as well as data from the UK
The U.S. Food and Drug Administration (FDA) authorized boosters of the Pfizer-BioNTech vaccine for older (age ≥ 65 years) and higher-risk adults in September 2021."
