mRNA vaccines stimulate lymph nodes for longer term protection; COVID-19 test accuracy may vary depending on time of day

(Reuters) – The following is a summary of some of the latest scientific studies on the novel 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

In addition to inducing antibodies for immediate defense, COVID-19 mRNA vaccines also stimulate lymph nodes to generate immune cells that provide long-term protection, a new study confirms. The first 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 plasma response,” said co-author Ali Ellebedy of Washington University School of Medicine in St. Louis. The immune cells that will produce antibodies upon exposure to the virus for years to come – called memory B cells – are generated by germline center B cells found only in lymph nodes near vaccine injection sites, His team explained in an article undergoing peer review for possible publication in a journal Nature. In repeated lymph node biopsies from volunteers, “we saw a robust response from the germinal center,” Ellebedy said. Responses lasted for at least seven weeks, “with no signs of slowing down anytime 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 center 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 swab test may vary depending on the time of day

The accuracy of baseline PCR tests of nasopharyngeal swab samples may vary depending on the time of day, new data suggests. The researchers analyzed 31,094 tests performed in symptomatic and asymptomatic individuals at 127 testing sites, including 2,438 tests that showed COVID-19. In an article published Saturday on medRxiv ahead of the peer review, they report that tests were more likely to be positive around 2 p.m. – and the proportion of positive tests in the early afternoon was twice as high as the lowest proportion observed at other times of the day. The study “suggests that people may 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 at night and early in the morning, ”said co-author Dr. Candace McNaughton. from Vanderbilt University. “If our results are confirmed, clinicians and public health teams could focus their efforts on reducing the risk of viral spread during peak periods of viral shedding,” she said. This could involve focusing on hiding the middle of the day to early afternoon at home while insulating, or encouraging early morning shopping for vulnerable populations. “There may be a greater benefit to repeating the tests if a negative test has been collected when viral shedding is generally less,” McNaughton said. (bit.ly/2NjcZiY)

Recommended surgery time after COVID-19

When possible, surgery should be delayed for at least seven weeks after infection with the novel coronavirus, and patients who still have symptoms at this stage may be given additional time, anesthesia researchers advise. They looked at data from 140,231 operated patients from 116 countries, including 3,127 with a history of COVID-19. The 30-day death rate 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 the diagnosis was made 5 to 6 weeks before surgery. preoperative. The death rate dropped to 2% when at least 7 weeks elapsed between diagnosis and surgery. For patients with persistent symptoms, the 30-day death rate was 6% even after 7 weeks, the researchers found. After adjusting for other risk factors, the odds of death increased 3.6-fold to 4.1 in patients operated on within six weeks of being diagnosed with COVID-19. “Patients with symptoms that persist for at least seven weeks after diagnosis may benefit from further delaying” their surgery, the researchers said. (bit.ly/3bLbFim)

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