Vaccination produces higher cord blood antibodies than COVID infection
JAMA Network Open published a new study yesterday showing higher cord blood COVID-19 antibodies in women who were vaccinated compared with those who were infected with COVID-19, suggesting vaccination produces more than 10-fold higher antibody concentrations in unborn babies compared to natural infections.
The study was based on patients who gave birth at Pennsylvania Hospital in Philadelphia between Aug 9, 2020, and Apr 25, 2021, a period encompassing when initial mRNA vaccine series became available, but before the approval of booster doses. In total, 585 pregnancies with cord blood serum samples were identified, including 169 patients who had been vaccinated but never infected and 408 who had been infected but not vaccinated.
The researchers also detected IgG antibodies to SARS-CoV-2 in the cord blood from more than 95% of newborns (557 of 585) in the study.
Those with maternal vaccination only had significantly higher antibody levels compared to the infection group, but transfer ratios, or how much the antibody levels in the cord blood match the antibody levels in the mother, were lower in the vaccinated group compared with the natural infection group, (0.80 [95% confidence interval CI, 0.68-0.93] vs 1.06 [95% CI, 0.98-1.14]; P < .001).
The authors said time to transfer was most affected by time since vaccination, with 8 weeks or more between vaccination and delivery producing the highest levels.
"These findings can inform optimal COVID-19 vaccination strategy during pregnancy," said senior author Karen M. Puopolo MD, PhD, of the Children's Hospital of Philadelphia and Chief of the Section on Newborn Medicine at Pennsylvania Hospital in a press release. "Patients should plan to get vaccinated with ample time before their due date, so that they – and their babies – can benefit from a robust immune response."
Nov 9 JAMA Netw Open study
Nov 9 Children's Hospital of Philadelphia press release
Israeli study shows fourth Pfizer dose protection wanes by 6 months
Yesterday in a letter to the New England Journal of Medicine, Israeli researchers reported an overall vaccine effectiveness of a fourth Pfizer COVID vaccine dose of 41% in the first 6 months, but they said protection decreased from 52% during the first 5 weeks after vaccination to no protection at 15 to 26 weeks.
The findings come from an ongoing prospective cohort study of healthcare workers vaccinated in Israel. Vaccine effectiveness was determined by comparing infection rates following the fourth dose (days 7 through 35, days 36 through 102, or days 103 through 181 after receipt of the fourth dose) to infections in those who received a third dose only, at least 4 months earlier.
"Antibody response peaked at approximately 4 weeks, waned to levels seen before the fourth dose by 13 weeks, and stabilized thereafter," the authors said.
The protection offered by a fourth dose was not as robust as the protection offered by a third dose, the authors said, with no substantial additional effectiveness over a third dose at 15 to 26 weeks after vaccination.
"These results suggest that the fourth dose, and possibly future boosters, should be timed wisely to coincide with disease waves or to be available seasonally, similar to the influenza vaccine. Whether multivalent booster doses will result in longer durability remains to be seen," the authors concluded.
Nov 9 N Engl J Med study