J&J vaccine efficacy lower, but protection remained more stable over time

Increased time since Covid-19 vaccination was associated with higher SARS-CoV-2 breakthrough infections and Covid-19 deaths among older adults during the time after the Delta variant became predominant in the United States in a newly published study.

Protection against infection declined among all age groups in recipients of two doses of the BNT162b2 and mRNA-1273 vaccines, as well as recipients of the single dose Ad26.COV2.S adenovirus vector vaccine.

Across all age groups and vaccine types included in the analysis, people vaccinated at least six months prior to August of this year (January or February 2021) were more than three times more likely to have breakthrough infection compared to those vaccinated in July of 2021.

The study findings, published online December 20 ahead of print in the soon-to-launch journal NEJM Evidence, from the New England Journal of Medicine group, “add to the evidence base that supports U.S. booster recommendations, especially in older adults,” wrote researcher Gabriela Paz-Baily, MD, of the U.S. Center for Disease Control and Prevention, and colleagues.

The analysis included Covid-19 case and death data from 15 geographically diverse U.S. states reported between early January and early September 2021, “used to estimate weekly hazard rates among fully vaccinated persons, stratified by age group and vaccine product.”

Case and death rates during August of 2021—soon after the SARS-CoV-2 Delta variant became dominant in the U.S.—were presented against four cohorts defined by vaccination month. Poisson modeling was used to estimate adjusted rate ratios comparing earlier cohorts to later rates.

Between Aug. 1 and Sept. 4, 2021, case rates per 100,000 person-weeks among all vaccine recipients for four time points—January to February, March to April, May to June, and July—were 168.8 (95% CI, 167.5- 170.1), 123.5 (95% CI, 122.8-124.1), 83.6 (95% CI, 82.9-84.3), and 63.1 (95% CI, 61.6-64.6), respectively.

“Similar trends were observed by age group for BNT162b2 and mRNA-1273 vaccine recipients,” the researchers wrote. “Rates for the Ad26.COV2.S vaccine were higher; however, trends were inconsistent.”

The risk for death among BNT162b2 vaccine recipients 65 years of age or older were higher among those vaccinated earlier in the year, compared to later in the year, while protection against death was sustained among the mRNA-1273 vaccine recipients.

“Across age groups and vaccine types, people who were vaccinated 6 months ago or longer (January-February) were 3.44 (95% CI, 3.36-3.53) times more likely to be infected and 1.70 (95% CI, 1.29-2.23) times more likely to die from Covid-19 than people vaccinated recently in July 2021,” the researchers wrote.

A similarly designed study conducted in Israel also showed waning immunity over time among BNT162b2 recipients.

The researchers noted that while the mRNA vaccines showed similar waning immunity over time, recipients of Johnson & Johnson’s Ad26.COV2.S vaccine did not show a consistent pattern of waning immunity across the study period, with the exception of younger recipients between the ages of 18 and 49 years.

“Higher case and death rates among recently vaccinated Ad26COV2 vaccine recipients may be explained by the single vaccine dose and relatively limited time for this group to develop robust antibody and cellular immune responses, compared with the mRNA vaccines,” the researchers wrote.

Study limitations cited by the researchers included the inability to adjust for different testing and prevention behaviors “by age and over time or for differences in local SARS-CoV-2 transmission to account for geographic heterogeneity,” as well as the inability to identify reinfections, and the potential impact of reduced access to testing early in 2021 which “may have resulted in a greater number of unrecognized infections in earlier cohorts.”

“As we only analyzed breakthrough cases occurring 14 days after completion of the primary series as defined, overall rates may be underestimated because some persons may have had a positive test result 0 to 13 days after the primary series and should have been removed from the at-risk set,” they wrote.

The researchers noted that the study findings are consistent with several earlier reports, and they concluded that these findings “underscore the likely value of boosters for certain high-risk groups, and continued use of non-pharmaceutical interventions, including among vaccinated persons.”

  1. Increased time since Covid-19 vaccination was associated with higher SARS-CoV-2 breakthrough infections and Covid-19 deaths among older adults during the time after the Delta variant became predominant in the United States.

  2. Across all age groups and vaccine types included in the analysis, people vaccinated at least six months prior to August of this year (January or February 2021) were more than three times more likely to have breakthrough infection, compared to those vaccinated in July of 2021.

Salynn Boyles, Contributing Writer, BreakingMED™

This research was funded by the U.S. Centers for Disease Control and Prevention.

Cat ID: 190

Topic ID: 79,190,730,933,190,31,926,192,561,927,151,928,925,934

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