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

(Reuters) – The following is a summary of some of the latest scientific studies on the new coronavirus and attempts 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, mRNA vaccines against COVID-19 also stimulate lymph nodes to generate immune cells that provide long-term protection, a new study confirms. The early wave of antibodies is generated by B cells called plasma blasts. In healthy volunteers, blood tests showed that two doses of the Pfizer / BioNTech vaccine “elicited a strong plasma blast response,” said study co-author Ali Ellebedy of Washington University School of Medicine in St. Louis. The immune cells that will produce antibodies in the coming years when exposed to the virus – called memory B cells – are generated by germinal center B cells that are only found in lymph nodes near vaccine injection sites, his team explained in a paper currently published by colleagues are assessed. possible publication in a Nature journal. On repeated biopsies of volunteers’ lymph nodes, “we saw a robust germ-center response,” Ellebedy said. The responses lasted for at least seven weeks, “with no sign of any short-term cooling,” he added. “Although we do not have long-term samples yet, given the magnitude and persistence of the germ center response, it is safe to assume that those individuals will develop a durable 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 gold standard PCR tests of nasopharyngeal swabs may vary by time of day, new data suggests. Researchers analyzed 31,094 tests performed on symptomatic and asymptomatic subjects at 127 test sites, including 2,438 tests showing COVID-19. In a paper posted to medRxiv on Saturday prior to peer review, they reported that tests were most likely to be positive around 2 p.m. – and the percentage of positive tests at the beginning of the afternoon was twice the lowest percentage found on 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 evening and early morning,” said co-author Dr. Candace McNaughton. from Vanderbilt University. “If our findings are confirmed, clinicians and public health teams can focus their efforts on lowering the risk of viral spread during times of peak viral shedding,” she said. This could include an emphasis on mid-day to early-afternoon home masking while isolating, or encouraging early morning shopping for vulnerable populations. “There may be more benefit in repeat testing if a negative test was collected when viral shedding is generally less,” said McNaughton. (bit.ly/2NjcZiY)

Surgery delay advised after COVID-19

If possible, surgery should be delayed for at least seven weeks after infection with the new coronavirus, and patients who still have symptoms at that point may benefit from further delay, advise researchers in Anesthesia. They reviewed data from 140,231 surgical patients from 116 countries, including 3,127 with a history of COVID-19. The death rate at 30 days after surgery was 1.4% in patients who had never had COVID-19. It was 9.1% in patients diagnosed within two weeks before surgery, 6.9% in those diagnosed within 3 to 4 weeks, and 5.5% when diagnosed 5 to 6 weeks preoperatively. The death rate fell to 2% if at least 7 weeks had passed between diagnosis and surgery. For patients with persistent symptoms, the 30-day death rate was 6%, even after a 7-week delay, researchers found. Adjusted for other risk factors, the risk of death was 3.6 to 4.1 times higher in patients who underwent surgery within six weeks of a COVID-19 diagnosis. “Patients with symptoms persistent for at least seven weeks after diagnosis may benefit from further delay” from their surgery, the researchers said. (bit.ly/3bLbFim)

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