Compared with the earlier Omicron BA.2 subvariant, currently dominant Omicron BA.5 is linked with higher odds of causing a second SARS-COV-2 infection regardless of vaccination status, a study from Portugal suggests.
From late April this year to early June, researchers studied 15,396 adults infected with the BA.2 variant and 12,306 infected with BA.5. The vaccines and boosters were equally effective against both sublineages, according to a report posted on medRxiv ahead of peer review.
However, 10% of BA.5 cases were reinfections, compared to 5.6% of BA.2 cases, which suggests a reduction in protection conferred by previous infection against BA.5 compared to BA.2, the researchers said. Moreover, the vaccines appeared to be less effective in reducing the risk of severe outcomes for BA.5 compared with BA.2.
“Among those infected with BA.5, booster vaccination was associated with 77% and 88% reduction in risk of COVID-19 hospitalisation and death, respectively, while higher risk reduction was found for BA.2 cases, with 93% and 94%, respectively,” the researchers wrote.
While “COVID-19 booster vaccination still offers substantial protection against severe outcomes following BA.5 infection,” they said, their findings provide “evidence to adjust public health measures during the BA.5 surge.”
Damage to heart cells
The spike protein on its surface that SARS-CoV-2 uses to break into heart muscle cells also triggers a damaging attack from the immune system, according to new research.
The SARS-CoV-2 spike protein interacts with other proteins in cardiac myocytes to cause inflammation, researchers said in a presentation at the American Heart Association's Basic Cardiovascular Sciences Scientific Sessions 2022.
In experiments with mice hearts, comparing the effects of SARS-CoV-2 spike proteins and spike proteins from a different and relatively harmless coronavirus, the researchers found that only the SARS-CoV-2 spike protein caused heart dysfunction, enlargement, and inflammation.
They found that in infected heart muscle cells, only SARS-CoV-2 spike interacted with the so-called TLR4 proteins (Toll-like receptor-4) that recognise invaders and trigger inflammatory responses. In a deceased patient with COVID-19 inflammation, the researchers found the SARS-CoV-2 spike protein and TLR4 protein in both heart muscle cells and other cell types. Both were absent in a biopsy of a healthy human heart.
"This means that once the heart is infected with SARS-CoV-2, it will activate the TLR4 signalling," Zhiqiang Lin of the Masonic Medical Research Institute in Utica, New York, said in a statement. "We provided direct evidence that spike protein is toxic to the heart muscle cells and narrowed down the underlying mechanism as spike protein directly inflames the heart muscle cells," he added.
Omicron infections
A new monoclonal antibody combination can prevent and treat Omicron infections in monkeys, researchers reported in Nature Microbiology.
The antibodies, called P2G3 and P5C3, recognise regions of the spike protein the SARS-CoV-2 virus uses to enter cells. “P5C3 alone can block all SARS-CoV-2 variants that had dominated the pandemic up to Omicron BA.2,” said Dr. Didier Trono of the Swiss Institute of Technology in Lausanne.”
