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


FILE PHOTO: The ultrastructural morphology exhibited by the 2019 novel coronavirus (2019-nCoV), which was identified as the cause of an outbreak of respiratory disease first detected in Wuhan, China, is seen in an illustration published by the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, USA January 29, 2020. Alissa Eckert, MS; Dan Higgins, MAM / CDC / Handout via REUTERS

(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 longer 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 plasmablast response,” said co-author Ali Ellebedy of Washington University School of Medicine in St. Louis. The immune cells that will produce antibodies after exposure to the virus in the next few years, called memory B cells, are generated by B cells from the germinal center that are found only in the lymph nodes near the vaccine injection sites, explained his team in an article currently under peer review for possible publication in a journal Nature. In repeat biopsies of the volunteers’ lymph nodes, “we saw a strong response from the germinal center,” Ellebedy said. Responses lasted at least seven weeks, “with no signs of cooling in the short term,” he added. “While 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 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 precision of gold standard PCR testing of nasopharyngeal swab samples may vary by time of day, new data suggests. 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 Saturday on medRxiv before peer review, they reported that tests were most likely to be positive around 2 p.m., and the proportion of positive tests in the early afternoon was twice the proportion lowest 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 night and early morning,” said the co-author, the Dr. Candace McNaughton. from Vanderbilt University. “If our findings are confirmed, physicians and public health teams could focus their efforts on reducing the risk of viral spread during times of peak viral shedding,” he said. That could involve emphasizing masking from noon to early afternoon at home while isolating yourself, or encouraging early morning shopping for vulnerable populations. “There may be a greater benefit to retesting if a negative test was obtained when viral shedding is generally less,” McNaughton said. (bit.ly/2NjcZiY)

Recommended delay in surgery after COVID-19

When possible, surgery should be delayed for at least seven weeks after infection with the new coronavirus, and patients who still have symptoms at that time may benefit from a longer delay, the researchers in Anesthesia advise. They reviewed data on 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 prior to surgery, 6.9% among those diagnosed within 3 to 4 weeks, and 5.5% when the diagnosis was made between 5 and 6 weeks before the operation. The mortality rate was reduced to 2% when at least 7 weeks had elapsed between diagnosis and surgery. For patients with continuous symptoms, the 30-day death rate was 6% even after a 7-week delay, the researchers found. After adjusting for other risk factors, the odds of death increased 3.6 to 4.1 times in patients who underwent surgery within six weeks of being diagnosed with COVID-19. “Patients with continuous symptoms at least seven weeks after diagnosis may benefit from a longer delay” of surgery, the researchers said. (bit.ly/3bLbFim)

Open tmsnrt.rs/3c7R3Bl in an external browser to see a Reuters graphic on vaccines in development.

Reporting by Nancy Lapid; Editing by Bill Berkrot

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