The items below are highlights from the free newsletter, “Smart, useful, science stuff about COVID-19.” To receive newsletter issues daily in your inbox, sign up here.

Many experts now agree that schools can re-open safely if they implement coronavirus control measures including mask wearing, physical distancing of three feet with masks on and six feet with masks off (per recently updated guidelines from the U.S. Centers for Disease Control), and good ventilation, reports Tanya Lewis at Scientific American (4/15/21). As of last month, "nearly half of U.S. school campuses were open,” Lewis writes. And school reopening in Florida, Utah and Missouri did not result in spikes in COVID-19 cases, research reveals. Studies of the effectiveness and safety of various makers’ COVID-19 vaccines in adolescents and young children are under way. Meanwhile, about 80 percent of school teachers and staffers are now fully or partially vaccinated, per the CDC, Lewis reports. “If schools require masking and do hand hygiene, the risk of mortality [for school staffers] from driving to work [and having a traffic accident] is higher for an unvaccinated adult than it is from acquiring COVID in school,” says a Duke University School of Medicine pediatrics researcher quoted in the piece. Air exchange in schools can be improved with upgrades to heating, ventilation and air-conditioning systems; opening windows; using fans; or changing air filters more frequently, the story states.

The U.S. Food and Drug Administration’s decision to pause the use of Johnson & Johnson’s one-shot COVID-19 vaccine “has set off a chain reaction of fear” about the safety of the vaccine and is causing “unnecessary drama” during a successful vaccination campaign in the U.S., writes Sam Baker at Axios (4/14/21). The clotting issue arose in six people, one of whom died from her blood clot, among the 7 million or so people who have received the Johnson & Johnson vaccine to date, per various sources. But “of the 20 most-engaged stories on social media about the Johnson & Johnson pause, just two headlines included the context that the blood clots were rare occurrences, according to data from NewsWhip," Baker writes. Pfizer says it can increase production of its COVID-19 vaccine to help fill gaps caused by the Johnson & Johnson pause, Baker writes.

The Unbiased Sci Pod posted a graphic on 4/13/21 that compares the percent risk of blood clots under four different scenarios or conditions—1) the Johnson & Johnson COVID-19 vaccine, 2) having COVID-19, 3) the incidence of clots in the general U.S. population, and 4) among people taking hormonal birth control. The figures are 0.000088%, 20% to 30%, 0.1% and 0.3% to 1%, respectively. Text below the graphic states, “Regulatory review by the CDC and FDA is doing what it should be doing; evaluating the relative risk of vaccination, assessing potential risk factors, and determining if there is a causal relationship. This does not mean the vaccine is unsafe or [that] you should be concerned if you’ve received the J&J vaccine.”

A similar issue with dangerous blood clots has arisen with AstraZeneca’s two-dose COVID-19 vaccine, as you’ve probably heard. The clotting problem with this vaccine also is very rare, but the vaccine is now “widely accepted” to cause (not just be linked to as is currently the case for the Johnson & Johnson vaccine) dangerous blood clots and low counts of the blood component called platelets, report Kai Kupferschmidt and Gretchen Vogel at Science (4/11/21). The AstraZeneca COVID-19 vaccine is in use in the UK and the European Union, and the World Health Organization has approved its use, “allowing it to begin distribution in low- and middle-income countries,” according to this 2/19/21 Forbes story. Doses have been delivered to more than 100 countries, and the vaccine is in use in Australia, Kupferschmidt and Vogel report. “In Europe, at least 222 suspected cases of the clots and low platelet counts have been reported among 34 million people who have received their first dose” of the AstraZeneca COVID-19 vaccine, the Science story states. And “more than 30 have died,” the story adds. “In the vast majority of cases,” the benefits of the vaccine outweigh the risks, researchers agree, the story states. Researchers are trying to determine the mechanism behind the clotting issue, which resembles a rare immune-system reaction to the drug heparin, the story states.

The U.S. Centers for Disease Control made it official on 4/5/21—the risk of infection with SARS-CoV-2 through touching a contaminated surface is “generally considered to be low,” less than 1 in 10,000, studies show. The primary way that the virus is spread is through inhalation of tiny virus-carrying droplets in the air in unventilated spaces. Cleaning surfaces with soap and water is enough to reduce the risk of infection by this route “in most situations,” the CDC page states. The CDC announcement vindicated many scientists and writers, including Derek Thompson at The Atlantic who coined the phrase “hygiene theater” last year. The phrase described the public-health energy wasted on deep-cleaning, particularly of surfaces in public settings, energy that could be directed more effectively toward distributing masks or public health messages about social distancing. In response to the new CDC update, Thompson wrote on 4/13/21, “You can put away the bleach, cancel your recurring Amazon subscription for disinfectant wipes, and stop punishing every square inch of classroom floor, restaurant table, and train seat with high-tech antimicrobial blasts.” Yet, many businesses, schools and transit systems still engage in “hygiene theater” with deep-cleanings or cash bans, Thompson writes. But “pandemic or no pandemic, you should wash your hands,” he adds.

Dr. Anthony Fauci, head of the U.S. Center for Allergy and Infectious Diseases since 1984, says he still will not travel, dine indoors at restaurants, go to the movies, or spend time with unmasked crowds indoors despite being vaccinated, reports Aylin Woodward at Insider (4/8/21). The only relaxation of SARS-CoV-2 precautions for Fauci is that he now is comfortable with small, unmasked, indoor gatherings at home, with what sounds like hugs allowed, the story suggests. Fauci’s concern reportedly is the uncertainty about whether vaccinated people can spread the virus if they get infected. “Fauci’s behavior aligns with [U.S. Centers for Disease Control] guidelines, which say that vaccinated Americans should continue to wear a mask in public at all times and avoid medium- and large-sized in-person gatherings,” writes Woodward. But Dr. Leana Wen, a Baltimore emergency physician, says the CDC guidelines for vaccinated people are overly cautious.

Sarah Zhang at The Atlantic explores the somewhat mysterious phenomenon of viruses—including SARS-CoV-2, MERS, flu, Ebola, West Nile, Epstein-Barr, polio, dengue, yellow fever and “original SARS”—that infect many of us without making us sick, that is, they cause asymptomatic infection (4/7/21). “Scientists now think that for viruses, a wide range of disease severity is the norm rather than the exception,” she adds. It’s difficult to study asymptomatic viral infections because people who don’t feel sick usually don’t go to the doctor, hospital or testing sites. But one recently published finding among 478 workers in Singapore found more “specific and coordinated” T-cells among infected people without symptoms than among infected people with symptoms. The researchers conclude in their study abstract, “…asymptomatic SARS-CoV-2 individuals are not characterized by weak antiviral immunity; on the contrary, they mount a highly functional virus-specific cellular immune response.” Another interesting T-cell item in Zhang’s piece pertains to “cross-reactivity": “Depending on where in the world you look, some 28 to 50 percent of people have T cells that predate the pandemic but nevertheless react to the new virus. These T cells may be remnants of infections with related coronaviruses.” Zhang concludes by noting that as SARS-CoV-2 continues to infect humans, both the virus and our immune systems will "learn new ways” to change in response to one another. “We’re at the very beginning of our relationship with this coronavirus.”

You might enjoy, “Insomnia: The Opera,” by Henry Alford, for The New Yorker (4/5/21).

This is an opinion and analysis article.