Researchers are looking for strong antibodies against many variants; breakthrough cases may be less infectious

August 23 (Reuters) – Here is a summary of some recent studies on COVID-19. They include research that warrants further study to corroborate the results and that has not yet been certified by peer review.

Researchers working on vaccine for many variants

Last week, two separate research teams reported on laboratory tests of monoclonal antibodies that appear to protect against a wide range of variants of the COVID-19 virus. A study, published Wednesday in The New England Journal of Medicine, identified “high-level, broad-spectrum” antibodies in blood samples from survivors of the initial SARS outbreak in 2003 who recently received Pfizer / BioNTech vaccine against SARS-CoV-2, the virus that causes COVID-19. In test-tube experiments, some of the antibodies from the SARS survivors induced by the vaccine could neutralize not only all of the current variants of SARS-CoV-2 of concern, but also five viruses that have been identified in bats and pangolins and which have the potential to cause human infection. In a separate study, published Thursday in the journal Immunity, another research team describes a highly protective antibody at low doses against a wide range of variants that cause COVID-19 in mice. “The antibody attaches to a part of the virus that differs little from variant to variant, which means that resistance is unlikely to occur there,” said the authors. The results of these studies could be a step towards the development of new antibodies that would be effective against several different coronaviruses, according to the two teams.

Shedding of infectious virus may be lower in breakthrough cases

Vaccinated people who are infected with COVID-19 have high levels of the virus in their nose and throat, but not all of this virus is infectious, a new study suggests. Of the 24,706 healthcare workers vaccinated in the Netherlands, 161 developed mild or asymptomatic breakthrough infections, mainly due to the Delta variant of the coronavirus. Viral levels on swab samples from the nose and throat of these patients were just as high as in unvaccinated healthcare workers who were infected with the original strain of the virus last year. But in test-tube experiments, the virus from vaccinated patients was less efficient at reproducing than the virus from unvaccinated patients, likely because some had been neutralized by antibodies from the vaccine, the researchers speculate. In a report published on medRxiv Saturday before the peer review, they conclude that shedding of the infectious virus is reduced in breakthrough cases, although patients are still contagious.

Antibodies fade faster after vaccine compared to actual infection

Protective antibody levels decline faster in recipients of Pfizer / BioNTech’s COVID-19 mRNA vaccine than in COVID-19 survivors, according to doctors at one of Israel’s largest HMOs. They monitored antibody levels in 2,653 adults who received two doses of the vaccine and in 4,361 never-vaccinated COVID-19 survivors. Antibody levels fell to 40% per month among vaccinated participants, compared to less than 5% per month among so-called convalescents. After six months, about 84% of vaccinees still had detectable antibodies, while about 90% of convalescents still had detectable antibodies after nine months. Dr Ariel Israel of Leumit Health Services, co-author of a report released on Sunday medRxiv before the peer review, noted that antibodies are not the only weapon of the immune system against the virus. Yet, he said, the data suggests that antibody protection in Pfizer vaccine recipients is declining at a greater rate than in COVID-19 survivors. Leumit researchers had Previously reported that breakthrough infection rates increase from about five months after vaccination. Dr Israel said the combined data argues for a booster injection five months after the second injection, especially for those at high risk.

Click for a Reuters chart on vaccines in development.

Reporting by Nancy Lapid; Editing by Tiffany Wu

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