This week's roundup of some of the latest scientific studies on the coronavirus and efforts to find treatments and vaccines for COVID-19 reinfection risks associated with the new coronavirus variants offers hope for mother-to-baby immunity and shows how evading serious illness may not be a good sign for neurological health.

Variant in Brazil more likely to reinfect survivors

A coronavirus variant circulating in Brazil is likely able to reinfect people who survived infections with earlier versions of the coronavirus, new data suggests, after the same concerns were voiced about the South African variant.

The variant that emerged in Brazil, called P.1, carries a mutation that is already known to make a variant prevalent in South Africa harder to treat with antibodies and harder to prevent with available vaccines. New data suggests that in many recovered patients, immunity to earlier versions of the virus will not afford immunity to P.1.

Researchers tested the neutralizing ability of antibodies in plasma samples taken from survivors of COVID-19 caused by earlier versions of the virus. The plasma "had sixfold less neutralizing capacity" against the P.1 variant than against earlier virus versions, the researchers reported on Monday ahead of peer-review on a preprint server belonging to The Lancet journal.

"Lower neutralization capacity of SARS-CoV-2 antibodies and partial immunity against new variants suggests that reinfection could occur in convalescent or even vaccinated individuals," the authors said.

In a separate paper posted on Wednesday on medRxiv ahead of peer review, some of the same researchers estimated that among every 100 survivors of COVID-19 due to earlier virus versions, 25 to 60 could become reinfected if exposed to the P.1 variant because their antibodies could not protect them. As of Thursday, according to the U.S. Centers for Disease Control of Prevention, there have been 13 cases of COVID-19 due to P.1 in the United States.

COVID-19 vaccine antibodies pass into breast milk

COVID-19 antibodies induced by vaccines from Pfizer Inc.-BioNTech and Moderna Inc. can pass into breast milk, a small study suggests, although it is not clear yet how long the antibodies will be present.

Six breastfeeding mothers who planned to receive both doses of the Pfizer-BioNTech or Moderna vaccines provided researchers with milk samples before and after vaccination, with the last sample collected two weeks after the second shot. None of the women had been infected with the coronavirus.

A week after the first shot, all of the women had COVID-19 antibodies in their breast milk. Antibody levels fell slightly afterward and then sharply increased after the second shot.

The two vaccines were similarly effective in inducing the antibodies, although antibody levels varied from woman to woman, the research team reported on medRxiv ahead of peer review.

"Further research is needed on the longevity of the antibody response in breast milk, as well as the magnitude and duration of effect on infant immunity to the virus," the researchers said.

Neurologic issues common in hospitalized children with COVID-19

Most children and adolescents are spared from severe COVID-19, but among those who do require hospitalization, temporary neurologic effects are common, researchers found.

In their study of 1,695 patients age 21 or younger hospitalized for COVID-19 or a COVID-19-related illness known as multisystem inflammatory syndrome, 365 – or 22% – had neurologic complications, including 43 (12%) with life-threatening neurologic disorders such as strokes and central nervous system infections. Other neurologic effects included seizures, headache, weakness, loss of smell and taste, and altered awareness or confusion.

Neurologic involvement in most patients was transient and resolved by the time they left the hospital, according to a report published on Friday in JAMA Neurology. Because they only studied hospitalized children, the range and rate of neurologic complications may be an underestimate of the actual issue, the authors said. They said more research is needed both to determine the true incidence and to track these children over the long term.