Vaccine response may be weaker in elderly; Merck drug shows promise in reducing virus level

The following is a roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for COVID-19, the illness caused by the virus.

Vaccine responses appear weaker in elderly

The COVID-19 vaccine from Pfizer Inc and German partner BioNTech SE induces weaker immune responses in elderly people compared to younger and middle-aged adults, new data suggest. Researchers studied 91 vaccine recipients under the age of 60 and 85 recipients over age 80. Seventeen days after the second of two doses, nearly one-third (31%) of the elderly recipients did not have any antibodies capable of neutralizing the virus. This was true for only 2% of the younger group, the researchers reported on Friday on medRxiv ahead of peer review. Even among those under age 60, only 16% had neutralizing antibodies after the first dose, the researchers found. "But that doesn't mean that the elderly should expect severe complications if they get infected," said coauthor Ortwin Adams of University Hospital Dusseldorf in Germany. "Recent reports from Israel, England and Scotland show that rates of hospitalization and severe disease progression are significantly lower than in the unvaccinated, even in people over 80 and even after the first COVID-19 vaccination," Adams said. "However, it could mean that the elderly need to be revaccinated sooner than young people to generate long-lasting protection. The results also suggest that transmissions may still be possible in some of the elderly after vaccination," he said, adding that "measures to effectively prevent transmissions should be continued." 

Merck antiviral drug may help speed viral clearance

An experimental antiviral drug being developed by Merck & Co and Ridgeback Biotherapeutics may help reduce viral loads in patients with early COVID-19, according to preliminary results from a clinical trial. Researchers presented their findings on Saturday at the 2021 Conference on Retroviruses and Opportunistic Infections but did not publish a formal report. In the 202-patient study, people who had been symptomatic for no more than 7 days and who were not hospitalized received either the oral antiviral molnupravir or a placebo. In data from fewer than half of the trial participants, after five days of treatment none of 47 patients taking molnupravir had positive viral cultures, compared to 6 of 25 patients (24%) taking the placebo. Merck said data on the drug's safety and effectiveness and additional secondary objectives of the study will be presented at an upcoming medical meeting.

Immune memory boosts COVID-19 survivors' vaccine response

New data provide a clue as to why some COVID-19 survivors may need only one dose of the two-dose Pfizer/BioNTech and Moderna Inc vaccines. Researchers tracked vaccine responses in 11 survivors of mild COVID-19 and 33 never-infected individuals. In everyone, the vaccines induced the immune system to produce antibodies along with so-called B cells that remember the virus and remain ready to produce new antibodies to fight it, although the magnitude of the B cell response was lower in older people. Those not previously infected "benefited from both doses," with additional antibody and memory B cell increases after the second shot, researchers reported on Saturday on medRxiv ahead of peer review. COVID-19 survivors, however, had significant responses to the first dose with no increase in antibodies or memory B cells after the second dose. Survivors' levels of memory B cells before vaccination correlated strongly with their antibody levels post vaccination, "indicating that these B cells were the likely source" of survivors' boosted antibody levels after just a single shot, said coauthor John Wherry of the University of Pennsylvania. This suggests memory B cells will play important roles if antibody levels fall over time, he added. Because memory B cells can be the source of new antibodies with some degree of "adaptability," they might play a role in immunity to variant viruses, he speculated.