The following is a summary of some recent studies on COVID-19. They include research that warrants further study to corroborate the findings and that has yet to be certified by peer review.
Vaccination plus prior COVID best protects against Omicron
People who were infected with an earlier version of the coronavirus and received three doses of an mRNA vaccine, such as the Pfizer PFE.N/BioNTech 22UAy.DE shot, appear to be best protected against symptomatic infection by the Omicron variant, according to a large study.
Studying more than one million people in Qatar during the Omicron wave in early 2022, researchers found that in unvaccinated people, immunity from infection with an earlier variant reduced symptomatic Omicron BA.2 infections by 46.1%, compared to unvaccinated people without previous infections. The effectiveness of inoculation by the Pfizer/BioNTech vaccine plus a recent booster, but without prior infection, was 52.2%, while a previous infection plus three mRNA vaccine doses – so-called hybrid immunity – was 77.3% effective against Omicron infection, according to a report published on Wednesday in The New England Journal of Medicine. Patterns were similar in recipients of Moderna’s MRNA.O mRNA vaccine.
“These findings demonstrate the benefits of vaccinating those with prior infection for optimal protection against the Omicron variant,” said coauthor Dr. Laith Abu-Raddad of Weill-Cornell Medicine – Qatar in a statement. While protection from the vaccine booster waned “rapidly,” protection from previous infection held fairly steady for nearly a year, his team found.
When Omicron did escape the body’s first lines of defense, any form of immunity – whether from vaccination or natural infection or both – “showed strong protection against Covid-19-related hospitalization and death, at an effectiveness of more than 70%.”
Neurological symptoms of COVID-19 can last months
COVID-19-related neurological symptoms, such as memory and concentration issues, can last half a year or more in some patients, according to a small study.
Among 27 patients who had such symptoms weeks after recovering from COVID-19, only nine reported complete resolution six months after joining the study, researchers reported on Wednesday in Annals of Clinical and Translational Neurology. The remaining 18 still had nervous system abnormalities – most often, impaired memory and trouble concentrating – although generally the symptoms had become less severe. “Some of these participants are high-level professionals who we’d expect to score above average on cognitive assessments, but months after having COVID-19, they’re still scoring abnormally,” Dr. Jennifer Graves of UC San Diego Health said in a statement. Most study participants had mild or moderate COVID-19. Graves said she suspects the neurological symptoms are caused by an immune response to the virus.
In four patients, her team saw a previously unidentified set of symptoms that included cognitive deficits, tremor and difficulty balancing. “These are folks who had no neurological problems before COVID-19, and now they have an incoordination of their body and possible incoordination of their thoughts,” said Graves. “We did not expect this.”
—Reporting by Nancy Lapid; Editing by Bill Berkrot
