Israeli study points to modest 4-dose vaccine protection against Omicron
Four-dose efficacy of mRNA vaccines against symptomatic Omicron COVID-19 infection is modest, according to a research letter yesterday in the New England Journal of Medicine that described a small study in Israel.
Of 1,050 eligible Israeli healthcare workers, 154 received a fourth dose of Pfizer and 120 received a fourth dose of Moderna. The researchers selected two age-matched controls from the remaining eligible participants for each person vaccinated.
The fourth dose produced a robust immune response and caused no concerning adverse events. Overall, 25.0% of the volunteers in the control group were infected with Omicron, compared with 18.3% in the Pfizer group and 20.7% in the Moderna group.
The researchers reported vaccine efficacy of 30% for Pfizer and 11% for Moderna for any SAR-CoV-2 infection, but neither vaccine achieved statistical significance for this measure. Vaccine protection against symptomatic COVID-19 was 43% for Pfizer and 31% for Moderna. Omicron accounted for 100% of circulating SARS-CoV-2 in Israel at the time of the study.
The authors note, "Our cohort was too small to allow for accurate determination of vaccine efficacy. However, within the wide confidence intervals of our estimates, vaccine efficacy against symptomatic disease was 65% at most."
They conclude, "A fourth vaccination of healthy young health care workers may have only marginal benefits. Older and vulnerable populations were not assessed." Also, they did not assess a fourth dose against severe COVID-19.
Mar 16 N Engl J Med study
Moms spread COVID-19 to newborns less than 2% of time, data show
SARS-CoV-2 is transmitted from mother to baby before, during, and after childbirth about 1.8% of the time, and vaginal births and breastfeeding do not raise the risk, finds a meta-analysis today in BMJ.
An international research team led by the University of Birmingham's World Health Organization Collaborating Centre for Global Women's Health analyzed data from 140 studies from around the globe that included 14,271 babies born to mothers with COVID-19. They found an overall COVID-19 infection rate of 1.8% (95% confidence interval, 1.2% to 2.5%), as determined by polymerase chain reaction (PCR) testing.
Of the 800 COVID-positive fetuses or babies with outcome data, 20 were stillbirths, 23 died during the first 28 days of life, and 8 were early pregnancy losses; 749 babies (93.6%) were alive at the end of follow-up.
The authors conclude, "Severe maternal covid-19 may be associated with SARS-CoV-2 positivity in babies, but not vaginal delivery, breastfeeding, or mother-baby contact after birth."
Senior author Shakila Thangaratinam, MD, PhD, professor of maternal and perinatal health at the University of Birmingham, said in a university news release, "Ours is the first study to use the World Health Organization's stringent methods to show that it is possible for the virus to be spread from the mother to baby while in the womb, during childbirth, and after delivery.
"However, parents and healthcare professionals can be reassured that only a very small proportion of babies born to mothers with SARS-CoV-2 test positive."
An editorial on the study in the same journal highlights widely varying quality of data among the studies analyzed but echoes Thangaratinam: "Overall, findings from this review seem reassuring."
Mar 17 BMJ study and editorial
Mar 17 University of Birmingham news release