In a new study from the University of Texas, researchers analyzed COVID infection by vaccination status among 780,225 Veterans.
They found that protection against any COVID-19 infection declined for all vaccine types, with overall vaccine protection declining from 87.9% in February to 48.1% by October 2021.
The decline was greatest for the Janssen (Johnson & Johnson) vaccine, with protection against infection declining from 86.4% in March to 13.1% in September
Declines for PfizerBioNTech were from 86.9% to 43.3%. Declines for Moderna were 89.2% to 58%.
Declines were assessed over the period February 1, 2021 to October 1, 2021, reflecting the emergence and dominance of the Delta variant in the U.S.
Patterns of breakthrough infection over time were consistent by age, despite rolling vaccine eligibility, implicating the Delta variant as the primary determinant of infection.
Importantly, vaccination of any type was protective against death among individuals who did become infected.
The relative benefit of vaccination for protection against death was greater for persons under 65 but was also very strong for persons over 65.
The study showed that the risk of death from COVID infection was highest in unvaccinated Veterans, regardless of age and comorbidities.
While some breakthrough infections resulted in death, vaccination remained protective against death in those who became infected during the Delta surge.
For those under 65 years old, vaccines overall were 81.7% effective against death.
Protection against death was greatest for the Pfizer vaccine, at 84.3%. Moderna was the next most effective, at 81.5%. Janssen was 73% effective.
For those 65 and over, overall vaccine effectiveness against death was 71.6%.
Moderna was 75.5% effective. Pfizer was 70.1% effective. Janssen was 52.2% effective.
This study gives researchers, policymakers and others a strong basis for comparing the long-term effectiveness of COVID vaccines.
It also gives 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 the chance of spread.
If you care about COVID vaccines, please read studies about COVID-19 vaccines effectively prevent hospitalization in older people and findings of COVID-19 vaccine booster dose can reduce infection in those 60 and older.
For more information about COVID vaccines, please see recent studies about should you get a third dose of COVID vaccine? and results showing that Moderna COVID-19 vaccine still effective after 6 months.
The study is published in Science. One author of the study is Dr. Barbara Cohn of PHI.
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