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COVID-19 didn't spread among school bus riders, Virginia study finds

A study yesterday in the Journal of School Health finds that while 39 elementary and high school students in a Virginia public school district rode school buses while infected with SARS-CoV-2, investigators found no evidence of viral transmission to other students or adults.

A team led by Eastern Virginia Medical School researchers tested all 1,154 in-person students in grades 1 to 12 every 1 or 2 weeks in the first 7 months of the 2020-21 school year, during the period of highest community transmission.

Fifteen school buses with 462 riders ran at near capacity, with two or three students in each seat and universal face coverings. Drivers were required to open the middle and last two bus windows 1 inch. There was no barrier between the driver and the first row of students. Each one-way ride ranged from 36 to 74 minutes.

The Centers for Disease Control and Prevention recommends physical distancing of at least 6 feet on public transportation but doesn't distinguish between public and school buses.

Thirty-seven students, one driver, and one aide rode the buses while infected with SARS-CoV-2, the virus that causes COVID-19, resulting in the quarantine of 52 students, none of whom tested positive 7 to 10 days later. Universal testing and contact tracing found no evidence of viral transmissions among students or adults from the bus.

"This study demonstrates a model for the safe operation of school buses while near capacity," the study authors wrote. "COVID-19 transmission can be low during student transport when employing mitigation including simple ventilation, and universal masking, at minimal physical distances and during the highest community transmission."

In a news release from Wiley, which published the journal, lead author Dana Ramirez, MD, noted that many public schools don't have enough buses and drivers to keep riders 6 feet apart or block off rows of seats. At the same time, as more students returned to in-person instruction, safe transportation became an equity issue, because many parents can't drive their children to school each day.

"We recognize that schools are under pressure to make data-driven operational decisions," Ramirez said. "We hope the model we describe and our data can be of assistance in demonstrating that school buses can safely operate at normal capacity even at high community COVID-19 case loads."

Real-world data show high effectiveness with mRNA COVID vaccines

Two case-control studies yesterday found high vaccine effectiveness (VE) after complete vaccination with the Pfizer/BioNTech or Moderna COVID vaccine, both of which are based on mRNA technology.

The first study matched 54,360 veterans with COVID-19 in the Veterans Affairs COVID-19 Shared Data Resource database with non-COVID veterans in the same system from Dec 15, 2020, to Mar 4, 2021. Less than one in five (18%) of those who were vaccinated tested positive for COVID-19; whereas, 32.8% who did not have COVID-19 were vaccinated. The researchers calculated that 7 days after the second dose, VE was 97.1% (95% confidence interval [CI], 96.6% to 97.5%), with Pfizer at 96.2% and Moderna at 98.2%.

VE remained above 95% regardless of sex, age-group, race, or comorbidity presence, the researchers write, noting that the cohort's median age was 61, 83.6% were male, and 62% were White.

Jul 20 Ann Intern Med study

The second study looked at COVID-19 cases in California from Feb 24 to Apr 29. The researchers matched people by age, sex, and geographic region from a pool of 525 adults infected with COVID-19 and 498 who were not (with at least 90% of each subgroup included in VE estimation). During the course of the study, the predominant COVID-19 strains went from B.1.427/429 (50% to 60%) to Alpha (B117, 49%).

Two weeks after receiving the second dose of COVID vaccine, VE was 87.0% for Pfizer and 86.2% for Moderna (95% CIs, 68.6% to 94.6% and 68.4% to 93.9%, respectively). Fully vaccinated participants receiving either showed 91.3% VE against symptomatic cases and 68.3% for asymptomatic cases (95% CIs, 79.3% to 96.3% and 27.9% to 85.7%, respectively).

All 18 people who were hospitalized for COVID-19 by the time of the researchers' telephone interview were either unvaccinated (15) or only partially vaccinated (3).

"Vaccine hesitancy among historically marginalized and rural populations, which account for a substantial proportion of all COVID-19 cases in California to date, presents a barrier to reaching coverage levels needed for herd immunity," the researchers add.

[Source: [Source: CIDRAP, The University of Minnesota, 21Jul21]

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