vaccines

As the delta variant became the dominant strain of coronavirus across the United States, all three COVID-19 vaccines available to Americans lost some of their protective power, with vaccine efficacy among more than 780,000 veterans dropping between 35% and 85%, according to a new study from the Public Health Institute, the Veterans Affairs Medical Center and the University of Texas Health Science Center. 

The decline was greatest for the Johnson & Johnson vaccine, with protection against infection declining from 86.4% in March to 13.1% in September. Declines for the Pfizer vaccine dropped to 43.3% in six months, from 86.9%, while Moderna’s protection fell from 89.2% to 58%.

Importantly, however, researchers also found that vaccination of any type was protective against death among infected individuals. The relative benefit of vaccination for protection against death was greater for persons under 65 but was also very strong for persons over 65.

For those under 65 years old, vaccines overall were 81.7% effective against death, with protection against death greatest for the Pfizer vaccine, at 84.3%. Moderna was the next most effective, at 81.5%, while Johnson & Johnson was 73% effective. For those aged 65 and over, overall vaccine effectiveness against death was 71.6%. Moderna was 75.5% effective, while Pfizer was 70.1% effective and Johnson & Johnson was 52.2% effective.

“Our study gives researchers, policy makers and others a strong basis for comparing the long-term effectiveness of COVID vaccines, and a lens for making informed decisions around primary vaccination, booster shots, and other multiple layers of protection, including masking mandates, social distancing, testing and other public health interventions to reduce chance of spread,” said Barbara Cohn, Ph.D., of PHI, and the lead author of the study.

The study was published in the journal Science.