(Reuters) – The following is a summary of some of the latest scientific studies on the new coronavirus and efforts to find treatments and vaccines for COVID-19, the disease caused by the virus.
MRNA vaccines stimulate lymph nodes for long-term protection
Along with the induction of antibodies for immediate defense, mRNA vaccines against COVID-19 also stimulate lymph nodes to generate immune cells that provide long-term protection, confirms a new study. The initial wave of antibodies is generated by B cells called plasmablasts. In healthy volunteers, blood tests showed that two doses of the Pfizer / BioNTech vaccine induced “a strong plasmablast response,” said co-author Ali Ellebedy of the Washington University School of Medicine in St. Louis. The immune cells that will produce antibodies after exposure to the virus in the coming years – called memory B cells – are generated by germinal B cells found only in lymph nodes near the vaccine injection sites, his team explained in an article today in peer review for possible publication in a Nature journal. In repeated lymph node biopsies from volunteers, “we saw a robust response from the germinal center,” said Ellebedy. The responses lasted at least seven weeks, “with no sign of cooling so soon,” he added. “Although we do not yet have long-term samples, it is safe to assume, given the magnitude and persistence of the germinal reaction, that these individuals will develop a lasting immune response” to mRNA vaccines. Moderna Inc’s vaccine also uses mRNA technology. (bit.ly/3tnAiYw)
The accuracy of the throat smear test may vary according to the time of day
The accuracy of gold standard PCR tests on nasopharyngeal smear samples may vary according to the time of day, new data suggest. The researchers analyzed 31,094 tests performed on symptomatic and asymptomatic individuals at 127 test sites, including 2,438 tests that showed COVID-19. In an article published on Saturday in medRxiv before the peer review, they reported that the tests were more likely to be positive by 2pm – and the proportion of positive tests in the early afternoon was twice that of the lowest proportion observed at other times of the day. The study “suggests that people can be more contagious at certain times of the day and raises questions about whether tests for SARS-CoV-2 may be less accurate when collected between late afternoon and early morning,” said the company. – author Dr. Candace McNaughton of Vanderbilt University. “If our findings are confirmed, doctors and public health teams can focus their efforts on reducing the risk of viral spread during the times of peak viral spread,” she said. This may involve emphasizing masking from noon to early afternoon at home while isolating, or encouraging early morning shopping for vulnerable populations. “There may be greater benefit in retesting if a negative test is collected when viral spread is generally less,” said McNaughton. (bit.ly/2NjcZiY)
Surgery delay advised after COVID-19
When possible, surgery should be postponed for at least seven weeks after infection with the new coronavirus, and patients who still have symptoms may benefit from further delay, advise the anesthesia researchers. They reviewed data from 140,231 surgical patients from 116 countries, including 3,127 with a history of COVID-19. The mortality rate at 30 days after surgery was 1.4% in patients who never had COVID-19. It was 9.1% among patients diagnosed within two weeks before surgery, 6.9% among those diagnosed within 3 to 4 weeks and 5.5% when diagnosis was made 5 to 6 weeks preoperatively. The death rate dropped to 2% when at least 7 weeks passed between diagnosis and surgery. For patients with continuous symptoms, the 30-day mortality rate was 6%, even after a 7-week delay, the researchers found. After adjusting for other risk factors, the chances of death increased 3.6 to 4.1 times in patients undergoing surgery within six weeks after the diagnosis of COVID-19. “Patients with continuous symptoms at least seven weeks after diagnosis can benefit from more delays” in the surgery, the researchers said. (bit.ly/3bLbFim)
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Nancy Lapid reporting; Bill Berkrot’s Edition