Researchers say that the single-dose Johnson & Johnson vaccine is 74% effective at preventing COVID-19 infection, even with variants of the coronavirus circulating. File Photo by Bill Greenblatt/UPI | License Photo
Nov. 2 (UPI) -- The one-dose Johnson & Johnson COVID-19 vaccine offers 74% protection against the virus, even with the more infectious Alpha and Delta variants in circulation, a study published Tuesday by JAMA Network Open found.
There were just 60 cases of COVID-19 among nearly 9,000 people who received the Johnson & Johnson vaccine at Mayo Clinic Health System facilities in Minnesota, Arizona, Florida, Wisconsin and Iowa between Feb. 27 and July 22, the data showed.
In comparison, there were more than 2,200 cases among nearly 90,000 unvaccinated people in the five states included in the analysis, the researchers said.
That equates to a nearly four-fold reduction in infections with "mass vaccination," they said.
"The primary take-home message is that the Ad26.COV2.S vaccine, known publicly as the Johnson & Johnson COVID-19 vaccine or one-dose vaccine, was over 73% effective against [COVID-19] infections," study co-author Tyler Wagner told UPI.
This effectiveness was "during the first five months after initial rollout, which is consistent with the clinical [trial]-reported efficacy of the one-dose vaccine," said Wagner, vice president of biomedical research at nference, a Cambridge, Mass.-based health technology and research firm.
The Johnson & Johnson COVID-19 vaccine is one of three cleared for use in the United States.
Unlike the other two, from Moderna and Pfizer-BioNTech, it requires one dose instead of two for full protection.
However, the one-dose shot also appears to be less effective at preventing infection with the virus than the other two, as it provided 85% protection against severe illness in early clinical trials.
Conversely, the Moderna and Pfizer-BioNTech two-dose vaccines have been found to be about 90% effective at preventing severe illness following infection, according to data from the Centers for Disease Control and Prevention.
In addition, the CDC and the Food and Drug Administration briefly halted distribution of the Johnson & Johnson vaccine in the spring after reports of blood clots in six out of about 8 million recipients.
The agencies reversed that decision 10 days later after determining that the risk for blood clots with the vaccine was "very low."
For this study, Wagner and his colleagues compared COVID-19 infection rates among 8,889 adults in 15 Midwestern and western states who received the Johnson & Johnson vaccine with those among 88,898 unvaccinated adults in those same states.
Cases of COVID-19 were confirmed using standard PCR testing, the researchers said.
Until the end of May, the Alpha variant was the most common virus strain in circulation in the states included in the analysis, accounting for up to 80% of cases.
However, by June and July, the Delta variant made up 40% to 50% of cases in these states, according to the researchers.
Nineteen of the 60 cases occurring in vaccinated participants were confirmed within 15 days of receipt of the shot.
The Johnson & Johnson vaccine takes "several weeks" following administration to reach "full effectiveness," the researchers said, citing earlier research.
"We cannot comment on the protection currently offered by the vaccine against the Delta variant," Wagner said.
However, "we will be continuing to monitor and report on the effectiveness and durability of the one-dose vaccine against the Delta variant in forthcoming studies," he said.