Mix-and-match booster shots shown more effective against Omicron strain
A letter yesterday in the New England Journal of Medicine (NEJM) from Centers for Disease Control and Prevention scientists shows homologous (same-vaccine) boosting for Johnson & Johnson (J&J) vaccine recipients was significantly less effective than mix-and-match booster doses when the Omicron strain was predominant in the United States.
Approximately 18 million Americans received the one-dose J&J vaccine as their primary COVID-19 vaccine. The study tracked COVID-19 cases among J&J recipients with no booster, a J&J booster, an mRNA booster, and adults who received three doses of mRNA vaccine (a primary series plus a booster).
The investigators collected data from Jan 2 to Mar 23, 2022, from the Increasing Community Access to Testing (ICATT) platform, which reported results from drive-through testing sites, and included adults who had reported vaccination status. The authors found vaccine effectiveness was highest for the regimens that included a booster dose of an mRNA vaccine and was lowest for those who received a single J&J shot.
Single-dose J&J efficacy was 17.8% (95% confidence interval [CI], 4.3% to 29.5%) compared to no vaccination from 14 days to 1 month after the shot, and 8.4% (95% CI, 1.5 to 14.8) from 2 to 4 months since receipt of the vaccine.
For recipients who received a J&J booster dose after a J&J primary vaccine, efficacy was 27.9% (95% CI, 18.3% to 36.5%) 14 days to 1 month after boost, and 29.2% (95% CI, 23.1% to 34.8%) 2 to 4 months after boost. In adults who received J&J plus an mRNA booster, efficacy was 61.3% (95% CI, 58.4% to 64.0%) and 54.3% (95% CI, 52.2% to 56.3%), similar to rates seen in those with three mRNA doses: 68.9% (95% CI, 68.3% to 69.5%) and 62.8% (95% CI, 62.2% to 63.4%).
"The results of this study suggest that a single booster dose of an mRNA Covid-19 vaccine in persons who received primary vaccination with single-dose Ad26.COV2.S [J&J] provided protection close to that of the three-dose mRNA vaccine regimen," the authors concluded.
May 25 NEJM letter
1 COVID vaccine dose may boost protection after infection, vaccination
Long-lasting yet flagging protection conferred by a previous COVID-19 infection or vaccination can be reinforced by even a single vaccine dose, concludes an Israeli study published yesterday in NEJM.
A team led by researchers from the Technion-Israel Institute of Technology in Haifa mined the Israeli Ministry of Health database for data on all patients who tested positive for COVID-19 or received any dose of the Pfizer/BioNTech vaccine from August to September 2021, when the Delta variant was dominant.
Adjusted COVID-19 incidence per 100,000 person-days rose over time since infection or vaccination. The rate increased from 10.5 among participants infected 4 to 6 months earlier to 30.2 among those infected at least 1 year before.
Among recipients of one vaccine dose after infection, the adjusted COVID-19 rate was 3.7 in those vaccinated less than 2 months before, rising to 11.6 in those vaccinated for at least 6 months or more. The rate of infection among COVID-naïve patients who received two vaccine doses less than 2 months before was 21.1, climbing to 88.9 among those vaccinated 6 months or more before.
Immunity against COVID-19 infection among previously infected participants faded over time, regardless of whether they had received any dose of vaccine before or after infection. "However, this protection was higher than that conferred after the same time had elapsed since receipt of a second dose of vaccine among previously uninfected persons," the researchers wrote. "A single dose of vaccine after infection reinforced protection against reinfection."
In an audio interview, NEJM Deputy Editor Lindsey Baden, MD, said that the goal of vaccination is not to eradicate SARS-CoV-2.
"What we want is to prevent people from getting severely ill, needing to be hospitalized, and one step further, to prevent illness that is disruptive to their lives, but I don't know that we're going to be able to stop [all] infections," he said. "That's a very high bar."
May 25 NEJM study and audio interview
World's second human H3N8 avian flu case reported in China
The Hunan Provincial Center for Disease Control and Prevention reported last week that a retrospective H3N8 avian flu case was confirmed in Changsha City in a 5-year-old boy, according to a report translated and posted today on Avian Flu Diary (AFD), an infectious disease news blog.
This case marks the world's second known infection from this particular avian flu strain, with the first case confirmed 1 month ago.
The boy with the latest infection developed a fever and chills on May 9 and recovered the next day. The agency did not list any possible exposure, such as live poultry. Changsha is the capital of Hunan province in southeastern China, south of Wuhan.
The first human case of H3N8 avian flu was confirmed by Chinese officials on Apr 26, and it involved a 4-year-old boy in Zhumadian City in Henan province, located more than 300 miles north of Changsha. On May 9 the World Health Organization provided more details on his case, noting that he had severe pneumonia and respiratory failure, but hadn't succumbed to the disease.
So far no human-to-human spread has been reported in either case.
May 26 AFD blog post
Apr 26 CIDRAP News scan and May 9 CIDRAP News story on first case
