Breakthrough infections can lead to long COVID; genes may explain critical illness in young, healthy adults--studies

(Reuters) - The following is a summary of some recent studies on COVID-19. They include research that warrants further study to corroborate the findings and that have yet to be certified by peer review.

Breakthrough infections can lead to long COVID:

The persistent syndrome of COVID-19 after-effects known as long COVID can develop after "breakthrough" infections in vaccinated people, a new study shows. Researchers at Oxford University in the UK reviewed data on nearly 20,000 U.S. COVID-19 patients, half of whom had been vaccinated. Compared to unvaccinated patients, people who were fully vaccinated - and in particular those under age 60 - did have lower risks for death and serious complications such as lung failure, need for mechanical ventilation, ICU admission, life-threatening blood clots, seizures, and psychosis. "On the other hand," the research team reported on medRxiv on Tuesday https://www.medrxiv.org/content/10.1101/2021.10.26.21265508v1 ahead of peer review, "previous vaccination does not appear to protect against several previously documented outcomes of COVID-19 such as long COVID features, arrhythmia, joint pain, Type 2 diabetes, liver disease, sleep disorders, and mood and anxiety disorders." The absence of protection from long COVID "is concerning given the high incidence and burden" of these lasting problems, they added.

Genes may explain critical COVID-19 in young, healthy adults:

A gene that helps the coronavirus reproduce itself might contribute to life-threatening COVID-19 in young, otherwise healthy people, new findings suggest. French researchers studied 72 hospitalized COVID-19 patients under age 50, including 47 who were critically ill and 25 with non-critical illness, plus 22 healthy volunteers. None of the patients had any of the chronic conditions known to increase the risk for poor outcomes, such as heart disease or diabetes. Genetic analysis identified five genes that were significantly "upregulated," or more active, in the patients with critical illness, of which the most frequent was a gene called ADAM9. As reported on Tuesday in Science Translational Medicine https://www.science.org/doi/10.1126/scitranslmed.abj7521, the researchers saw the same genetic pattern in a separate group of 154 COVID-19 patients, including 81 who were critically ill. ...

Women who get the first dose of an mRNA COVID-19 vaccine while pregnant or breastfeeding need the second dose to bring their protective benefit up to normal, according to a new study. Researchers compared immune responses to the mRNA vaccines from Moderna Inc or Pfizer Inc and partner BioNTech SE in 84 pregnant women, 31 breastfeeding women, and 16 similarly-aged nonpregnant, non-lactating women. After the first shot, everyone developed antibodies against the coronavirus. But antibody levels were lower in women who were pregnant or breastfeeding. Other features of the immune response also lagged in the pregnant and lactating women after the first dose but "caught up" to normal after the second shot. ...

Obesity is a known risk factor for more severe COVID-19. One likely reason may be that the virus can infect fat cells, researchers have discovered. In lab experiments and in autopsies of patients who died of COVID-19, they found the virus infects two types of cells found in fat tissue: mature fat cells, called adipocytes, and immune cells called macrophages. ...