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The following is a summary of some of the latest scientific studies on the novel coronavirus and efforts to find cures and vaccines for Covid-19, the disease that caused the virus.
MRNA vaccines stimulate lymph nodes for long-term protection
Along with stimulating antibodies for immediate protection, mRNA vaccines against Covid-19 also stimulate the lymph nodes to generate immune cells that provide protection over the long term, a new study confirms.
The early wave of antibodies is formed by B cells called plasmablasts. In healthy volunteers, blood tests showed that two doses of the Pfizer / BioNTech vaccine stimulated a “strong plasmablast response,” said co-author Ali Ellebedy of the University of Washington School of Medicine in St. Louis. Louis.
The immune cells that produce antibodies when they appear on the virus in the coming years – called B-memory cells – are generated by germinal B cell cells that are only found in lymph nodes near vaccine injection sites, the his team in a paper that is currently peer-reviewed for possible publication in the journal Nature. In repeated biopsies of voluntary lymph nodes, “we saw a strong germinal center response,” Ellebedy said.
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The responses lasted at least seven weeks, “with no sign of cooling down anytime soon,” he said. “Although we do not yet have long-term samples, it is safe to assume that the size and stability of the germinal center will allow these individuals to develop a stable immune response to mRNA vaccines. Moderna Inc vaccine also uses mRNA technology.
The accuracy of a throat swab test can vary depending on the time of day
The accuracy of gold-standard PCR tests of nasopharyngeal swab samples can vary depending on the time of day, new data suggest. Researchers analyzed 31,094 trials performed in symptomatic and asymptomatic individuals at 127 test sites, including 2,438 trials that showed Covid-19.
In a paper posted Saturday on medRxiv ahead of peer review, the report tests were more likely to be positive around 2pm – and the proportion of positive tests in the early afternoon was twice as high as their ‘lowest proportion seen 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 so inaccurate when collected between the end of the day. afternoon and early morning, “said co – author Dr Candace McNaughton of Vanderbilt University.
“If our findings are confirmed, clinicians and public health teams could focus their efforts on reducing the risk of viral transmission at times of peak viral exposure,” she said. That could mean stressing midday to early afternoon shelter at home while alone, or encouraging early morning shopping for vulnerable populations.
“There may be more benefit in retesting if a negative test was collected when viral shearing is typically less common,” McNaughton said.
Surgical delay advised after Covid-19
Whenever possible, surgery should be delayed for at least seven weeks after infection with the new coronavirus, and patients who still have symptoms at that stage may benefit from further delays, counseling in Anesthesia.
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They reviewed data on about 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 had never received 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% at diagnosis do 5 to 6 weeks in advance.
The mortality rate dropped to 2% when at least 7 weeks had elapsed between diagnosis and surgery. For patients with persistent symptoms, the 30-day mortality rate was 6% even after a 7-week delay, researchers found.
After adjusting for other risk factors, death rates increased 3.6-to-4.1-fold in patients undergoing surgery within six weeks of Covid-19 diagnosis. “Patients with persistent symptoms at least seven weeks from the time of diagnosis may benefit from further delay” of their surgery, the researchers said.