No vaccine provides perfect protection, and so-called breakthrough infections after coronavirus vaccination are rare and unlikely to lead to serious illness. The CDC COVID-19 Vaccine Breakthrough Case Investigations Team published analysis of breakthrough infections reported through April 30. The study, published in the CDC’s MMWR, includes 10,262 breakthrough infections from 46 states. From preliminary data, 27% of breakthrough cases were asymptomatic, 10% were hospitalized, and 2% died. Of the hospitalized cases, 29% were asymptomatic or hospitalized for a reason other than COVID-19. Sequence data were available for only 5% (555 cases) of cases, 64% of which identified variants of concern: B.1.1.7 (56%), B.1.429 (25%), B.1.427 (8%), P.1 (8%), and B.1.351 (4%). The University of Washington Virology Lab (UWVL) also found variants of concern to be responsible for breakthrough infections. They sequenced 20 vaccination breakthrough infections from UW Medicine and found that all 20 cases were classified as variants of concern. As of May 1, the CDC is no longer investigating all vaccine breakthrough infections, instead focusing only on hospitalized and fatal cases. Vaccine effectiveness studies will continue, but only in limited populations.
In a study, published in bioRxiv (preprint), researchers from Rockefeller University (New York) report on a cohort of 63 COVID-19-convalescent individuals assessed at 1.3, 6.2, and 12 months after infection, 41% of whom also received mRNA vaccines. In individuals who were not vaccinated, neutralizing activity and a specific type of memory B cells remained relatively stable from 6 to 12 months. Notably, vaccination increased all components of the humoral response and resulted in serum neutralizing activities against variants of concern that are comparable to or greater than neutralizing activity against the original SARS-CoV-2 strain achieved by vaccination of naïve individuals. The data suggest that immunity among recovered COVID-19 patients likely will be very long lasting, and those who receive mRNA vaccines should produce enough antibodies and memory B cells to provide protection against circulating SARS-CoV-2 variants. The researchers speculate this is evidence to consider boosters for non-convalescent but vaccinated individuals as new variants of concern emerge.
CSSE is reporting 33,235,632 positive cases in the U.S. and 593,870 deaths. DOH reported 2,320,818 confirmed cases in Florida Friday, with 36,774 deaths.