August 2. Delta breakthrough infections likely contagious
Among people infected by the Delta variant of the coronavirus, fully vaccinated people with “breakthrough” infections may be just as likely as unvaccinated people to spread the virus to others, new research suggests. The higher the amount of coronavirus in the nose and throat, the more likely the patient will infect others. In one Wisconsin county, after Delta became predominant, researchers analyzed viral loads on nose-and-throat swab samples obtained when patients were first diagnosed. They found similar viral loads in vaccinated and unvaccinated patients, with levels often high enough to allow shedding of infectious virus.
The Lambda variant of the coronavirus, first identified in Peru and now spreading in South America, is highly infectious and more resistant to vaccines than the original version of the virus the emerged from Wuhan, China, Japanese researchers have found. Although it is not clear yet whether this variant is more dangerous than the Delta now threatening populations in many countries, senior researcher Kei Sato of the University of Tokyo believes “Lambda can be a potential threat to the human society.”
Among fully vaccinated people who never had COVID-19, getting a third dose of an mRNA vaccine from Pfizer (PFE.N)/BioNTech or Moderna (MRNA.O) would likely increase levels of antibodies, but not antibodies that are better able to neutralize new virus variants, Rockefeller University researchers reported on Thursday on bioRxiv ahead of peer review. They note that in COVID-19 survivors, the immune system’s antibodies evolve during the first year, becoming more potent and better able to resist new variants. In 32 volunteers who never had COVID-19, they found that antibodies induced by mRNA vaccines did evolve between the first and second shots. But five months later, vaccine-induced antibodies were “equivalent” to those seen after the second dose, with “little measurable improvement” in the antibodies’ ability to neutralize a broad variety of new variants, said coauthor Michel Nussenzweig.