Fourth COVID vaccine dose boosts protection against infection, severity
A study in Israel during the Omicron variant surge finds that rates of COVID-19 infection and severe illness were lower after a fourth dose of the Pfizer/BioNTech vaccine than after three doses, and while protection against infection waned quickly after 4 weeks, protection against severe disease was still strong at 6 weeks.
The study, published yesterday in the New England Journal of Medicine (NEJM), involved data from 1,252,331 people aged 60 years and older, who became eligible for a fourth COVID-19 shot in Israel on Jan 2, 2022. The study period ran from Jan 10 to Feb 18 for severe illness and to Mar 2 for infection.
The unadjusted rate of COVID-19 infections per 100,000 person-days among people who had received a fourth vaccine dose 8 days before was 1.5, compared with 3.9 in those who had received three doses and 4.2 in controls who had received a fourth dose 3 to 7 days before.
After adjustment, the rate of severe COVID-19 in the fourth week after receipt of the fourth vaccine dose was lower than that of the three-dose group by a factor of 3.5 (95% confidence interval [CI], 2.7 to 4.6) and lower than that in controls by a factor of 2.3 (95% CI, 1.7 to 3.3).
Vaccine protection against severe infection was stable for 6 weeks after the fourth dose. The unadjusted rate of severe COVID-19 infection per 100,000 person-days was 177 in fourth-dose recipients, 361 in the three-dose group, and 388 in controls.
The adjusted rate of infection among those who had received a fourth dose 4 weeks earlier was lower than that in the three-dose group by a factor of 2.0 (95% CI, 1.9 to 2.1) and lower than that of controls by a factor of 1.8 (95% CI, 1.7 to 1.9).
"These analyses provided evidence for the effectiveness of a fourth vaccine dose against severe illness caused by the omicron variant, as compared with a third dose administered more than 4 months earlier," the researchers wrote. "For confirmed infection, a fourth dose appeared to provide only short-term protection and a modest absolute benefit."
Apr 5 NEJM study
C-sections, inductions dropped during first months of COVID-19
Fewer in-person prenatal visits during the first months of the COVID-19 pandemic resulted in a 6.5% drop in premature caesarian sections (C-sections) and inductions, according to a new study in Pediatrics. The research was conducted by a team at Georgia Tech's School of Economics.
This is the first major study to examine pandemic-era birth data at scale, the authors say, and it raises questions about how and if some medical interventions may unnecessarily result in preterm deliveries.
The study was based on 39 million US births from 2010 through 2020. Using data from the National Center for Health Statistics, researchers forecasted expected premature births—babies born before 37 weeks of pregnancy—from March to December of 2020, and compared these to actual outcomes seen during those months.
From March 2020 to December 2020, the number of preterm births from C-sections or induced deliveries remained 0.35 percentage points below the predicted values, which meant 350 fewer preterm C-sections and induced deliveries per 100,000 live births, or 10,000 fewer overall during the study period, the authors said.
"While much more research needs to be done, including understanding how these changes affected fetal deaths and how doctors triaged patient care by risk category during the pandemic, these are significant findings that should spark discussion in the medical community," Daniel Dench, PhD, lead of author of the study, said in a Georgia Tech press release.
Apr 6 Pediatrics study
Apr 6 Georgia Tech press release