Unvaccinated at up to 4 times the risk of symptomatic COVID infection
People unvaccinated against COVID-19 were at up to four times the risk of infection, finds a JAMA Network Open study based on tests taken at US retail pharmacies, most of them after the emergence of the Delta (B1617.2) variant.
Researchers from CVS Health in Rhode Island analyzed the incidence of symptomatic COVID-19 infections diagnosed in 1,237,097 adults at 4,094 CVS pharmacies from May 1 to Aug 7, 2021. Median patient age was 37 years.
Of the 1,237,097 adults, 52.2% were unvaccinated and 47.8% were vaccinated. Of the vaccinated, 56.7% had received the Pfizer/BioNTech (BNT162b2) COVID-19 vaccine, while 35.0% received Moderna (mRNA-1273), and 8.3% received Johnson & Johnson (J&J).
Adjusted estimated vaccine effectiveness against COVID-19 infection for those who had received two doses of the Moderna or Pfizer mRNA vaccines peaked after 2 weeks (96.3% for Moderna, 92.4% for Pfizer), then declined to 86.8% and 78.6%, respectively, at 2 to 3 months and 74.2% and 66% after 6 months in multivariable analyses. Adjusted vaccine effectiveness for one dose of the J&J vaccine remained higher than 50% after 2 weeks.
Patients who received the Pfizer or Moderna vaccines had the lowest incidence of COVID-19 infection throughout the study, while the unvaccinated had the highest. The unvaccinated had 412% more infections than those who received the Moderna vaccine, 287% more than those who received the Pfizer vaccine, and 159% more than J&J recipients.
Incidence of COVID-19 infection was 24.8% among the unvaccinated, 15.6% in the J&J group, 8.6% in the Pfizer group, and 6.0% among Moderna recipients. In July and August, the risk of infection in both unvaccinated and vaccinated participants increased with the rising incidence of Delta cases.
The researchers noted that the cases included in the study were likely less severe, given that they were diagnosed at a retail pharmacy.
"Although our data indicate that vaccine effectiveness gradually wanes over time, the 2-dose mRNA vaccines remained estimated 74% (mRNA-1273) and 66% (BNT162b2) effective against symptomatic SARS-CoV-2 infections 6 months or longer after 2 doses during a period in which the Delta variant became the dominant strain," they wrote.
Dec 22 JAMA Netw Open research letter
Convalescent plasma cuts COVID hospital cases in half, clinical trial shows
Early treatment with concentrated convalescent plasma halved the need for hospitalizations for COVID-19 outpatients, according to a randomized, controlled trial published yesterday on the preprint server medRxiv.
The study, led by Johns Hopkins University researchers and not yet peer-reviewed, compared the effectiveness of concentrated (high-titer) convalescent plasma to a placebo in 1,225 symptomatic adult COVID-19 patients at 23 US sites. Convalescent plasma from blood donated by COVID-19 survivors is rich with antibodies against SARS-CoV-2 infection.
Of the 1,225 patients randomly assigned to convalescent plasma or placebo from Jun 3, 2020, to Oct 1, 2021, 1,181 received a transfusion within 9 days of COVID-19 symptom onset. Median patient age was 44 years, 7% were at least 65 years old, 35% were 50 or older, 57% were women (including 3 who were pregnant), Black and Hispanic participants each made up over 10% of the population, and 2% were American Indian or Native Pacific Islander.
Thirty-seven of 589 (6.3%) who received a placebo were hospitalized within the following 28 days, compared with 17 of 592 (2.9%) who received convalescent plasma, for a relative risk of 0.46, corresponding to a 54% risk reduction.
The trial was stopped early after enrolling over 90% of its target after fewer hospitalizations were observed among participants (5 to 6 hospitalizations among the first 1,000 enrollees, versus less than 1 per 100 enrollees thereafter).
"Early administration of high titer SARS-CoV-2 convalescent plasma reduced outpatient hospitalizations by more than 50%," the study authors wrote. "High titer convalescent plasma is an effective early outpatient COVID-19 treatment with the advantages of low cost, wide availability, and rapid resilience to variant emergence from viral genetic drift in the face of a changing pandemic."
In a Johns Hopkins news release, co-lead author Kelly Gebo, MD, MPH, said that concentrated convalescent plasma is another tool in the COVID-19 armamentarium. "We believe that the best role for COVID-19 high-titer convalescent plasma is extending its use to early outpatient treatment when other therapies, such as monoclonal antibodies or drugs, are either not readily available—as in low- and middle-income countries—or ineffective—as with SARS-CoV-2 variants that are resistant to certain monoclonal antibodies," she said.
Dec 21 medRxiv study
Dec 21 Johns Hopkins news release
Study finds COVID-19 vaccination in pregnancy passes antibodies to baby
Yesterday a study in JAMA Pediatrics suggested that COVID-19 vaccination in the second trimester of pregnancy was associated with a maternal humoral antibody response that is sustained during labor and transfers antibodies to the newborn.
The cohort study of 130 pregnant women, who completed the Pfizer-BioNTech vaccine series in the second trimester of pregnancy, were seen in Haifa, Israel, from May to July 2021. The mean gestational age at administration of the second vaccine dose was 24.9 weeks.
Antibody levels were tested in newborns within 30 minutes of delivery, with 100% of those tested showing positive results. According to the authors, neonatal IgG titers were 2.6 times higher than maternal titers (median [range], 3315.7 [350.1 to 17,643.5] AU/mL vs 1185.2 [146.6 to 32,415.1] AU/mL), and a positive correlation was seen between maternal and neonatal antibodies (r = 0.92; 95% confidence interval, 0.89 to 0.94).
"Univariable analysis demonstrated correlation of maternal and newborn SARS-CoV-2 IgG [immunoglobulin G] antibody titers at delivery with maternal age, gestational age at the second vaccine dose, and duration from the second vaccine dose to birth," the authors said.
For each 1-year increase in the maternal age, antibody levels in both mothers and babies dropped by 3.9%. For each 1-week increase in gestational age at the second vaccine dose, maternal and newborn antibody levels increased by 10.5%.
"The current study found a maternal and newborn immune response at birth associated with vaccination during the second trimester, suggesting an advantage of early vaccination during pregnancy rather than during the third trimester," the authors concluded.
Dec 21 JAMA Pediatr study