COVID-19 Vaccines: AstraZeneca & B.1.351 / Response in Transplant Recipients / Moderna & Young Children

By Kelly Young

Edited by David G. Fairchild, MD, MPH, and Lorenzo Di Francesco, MD, FACP, FHM

Here are some of the latest developments on COVID-19 vaccines:

AstraZeneca vaccine & B.1.351 variant: AstraZeneca's COVID-19 vaccine does not appear to prevent infection from the B.1.351 variant, according to a study in the New England Journal of Medicine. Roughly 2000 HIV-negative adults in South Africa were randomized to receive two doses of the ChAdOx1 vaccine or placebo. The vaccine had an efficacy of only 22% for mild-to-moderate COVID-19. Over 90% of cases were caused by the B.1.351 variant; vaccine efficacy against this variant was just 10%. Serum samples from 25 participants were tested against pseudoviruses and live viruses with the B.1.351 strain. Most vaccine recipients had no neutralization activity against the variant.

Vaccine response in transplant recipients: Organ transplant recipients have low antibody responses to COVID-19 mRNA vaccines, according to a JAMA study. Researchers tested antibody responses in over 400 transplant recipients a median of 20 days after receiving one dose of an mRNA vaccine. Antibodies were detectable in just 17% of participants. Those who were not taking anti-metabolite maintenance immunosuppression therapy, younger recipients, and those who received the Moderna mRNA-1273 vaccine were more likely to develop a response than others. The authors conclude: "These findings of poor antispike antibody responses in organ transplant recipients after the first dose of mRNA vaccines suggest that such patients may remain at higher early risk for COVID-19 despite vaccination."

Moderna vaccine & young children: Moderna says it has begun testing its mRNA vaccine in children aged 6 months through 11 years. It expects to enroll roughly 6800 children in this phase 2/3 study. The vaccine is currently authorized for use in adults aged 18 and up, and a trial is planned for youth aged 12 through 17 years.