A study finds that inflammation from Covid-19—not the coronavirus itself—may be the cause of a loss of smell in Covid-19 patients, CDC data shows some people who had been infected by delta were also later infected by omicron, and more in this week's roundup of Covid-19 news.

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• The rates of myopericarditis after Covid-19 vaccination were relatively low and comparable to rates seen in other types of vaccinations, according to a systemic review and meta-analysis published in Lancet Respiratory Medicine. For the analysis, researchers examined 22 studies from Jan. 1, 1947, to Dec. 31, 2021, that included over 400 million vaccine doses to determine the incidence of myopericarditis after receiving Covid-19 vaccines compared with non-Covid vaccines. Overall, rates of myopericarditis after vaccination were 33 cases per million doses, with the highest rates being after smallpox vaccination at 132.1 cases per million doses. For Covid-19 vaccines, the rate of myopericarditis was 18.2 cases per million doses. The rate was higher among those who received mRNA Covid-19 vaccines (22.6 cases per million doses), who were younger than 30 (40.9 per million), or were male (23 per million). "The occurrence of myopericarditis following non-Covid-19 vaccination could suggest that myopericarditis is a side effect of the inflammatory processes induced by any vaccination and is not unique to the SARS-CoV-2 spike proteins in Covid-19 vaccines or infection," said Jyoti Somani, a co-author of the study from National University Hospital in Singapore. (Walker, MedPage Today, 4/11)

• According to a new postmortem study published in JAMA Neurology, inflammation, rather than the coronavirus itself, may be behind the loss of smell commonly experienced by Covid-19 patients. For the study, researchers examined the olfactory bulb at the base of the brain in 23 deceased Covid-19 patients and 14 matched controls who died of other causes between April 7, 2020, and Sept. 11, 2021. Overall, three of the Covid-19 patients had lost their sense of smell, while four had an impaired ability to smell, and two lost both their sense of smell and taste. No controls had lost their sense of smell or taste. Using light and electron microscopy, the researchers looked for any genetic material from the coronavirus and assessed cell structures and characteristics, as well as blood vessels and the neurons in them. They also determined the number of axons in the neurons, which contribute to sensory perception and movement. Information about the deceased patients' sense of smell and taste was gathered from either medical records or family interviews. According to Cheng-Ying Ho, an associate professor of pathology at the Johns Hopkins University School of Medicine and the study's lead author, the Covid-19 patients, particularly those whose senses of smell were impacted, had more severe vascular injury and fewer axons in the olfactory bulb, "strongly suggesting that these effects aren't age related and therefore, are linked to SARS-CoV-2 infection." However, despite the nerve and vascular damager, most of the Covid-19 patients had no detectable coronavirus particles in their olfactory bulb. "Our findings suggest that SARS-CoV-2 infection of the olfactory epithelium leads to inflammation, which in turn, damages the neurons, reduces the numbers of axons available to send signals to the brain, and results in the olfactory bulb becoming dysfunctional," Ho said. In an interview with JAMA Neurology, Ho said that the long-term loss of smell seen in around 1% of Covid-19 patients may be preventable. "If inflammation is the major cause of the injury in olfactory structures, it is possible that we may be able to use anti-inflammatory agent as the treatment," she said. (CIDRAP News, 4/12; Johns Hopkins Medicine, Eureka Alert, 4/11)

• Veru Inc. on Monday announced that their experimental Covid-19 drug sabizabulin was able to halve the death rate for hospitalized Covid-19 patients who were receiving supplemental oxygen and were at high risk for serious lung disease and death. In a clinical trial of hospitalized patients, 52 participants were given a placebo and regular care, while 98 participants received regular care and sabizabulin once a day for up to 21 days. Overall, around half of the placebo group died within 60 days, while only 20% of the treatment group died within the same period. According to the New York Times, these findings, which have not yet been peer-reviewed, led independent safety monitors to recommend stopping the trial early, which Veru did last week. "Sabizabulin is the first drug to demonstrate a clinically and statistically meaningful reduction in deaths in hospitalized patients," said Veru CEO Mitchell Steiner. "This represents a big step forward." The company said it plans to meet with FDA later this month and will apply for emergency use authorization of its drug. (Rabin, New York Times, 4/11)

• Some people who were infected with the delta variant were later infected with the omicron variant less than three months later, according to new CDC research. In particular, researchers found that 10 people, including eight children and two adults, tested positive for Covid-19 and had confirmed delta and omicron infections within 90 days. Among the children, the median age at first infection was 11 years, and five were male. Of the two adults, one was a woman living in a long-term care facility (age group 65-74), and the other was a female health care worker (age group 25-39). Overall, seven of the 10 patients were unvaccinated, with the only the health care worker and two children either being fully or partially vaccinated. The interval between the two infections ranged from 23 to 87 days, with a median of 54.5 days. According to the researchers, because most of the patients were children, they "might have had increased risk for SARS-CoV-2 infection because of low vaccination rates and high rates of close contact in school-aged cohorts, and higher frequency and intensity of exposures in health care and congregate settings." The researchers added that most reinfections likely go unidentified due to limited capacity for variant testing and whole-genome sequencing, as well as growing use of at-home antigen tests. (Walker, MedPage Today, 4/8)

• Pfizer and BioNTech on Thursday reported that a booster dose of their Covid-19 vaccine significantly increased neutralizing antibodies in children ages 5 to 11. The dosage for this age group is a third of the dose given to individuals ages 12 and older. In a small study, 140 children ages 5 to 11 who had received two doses of the Pfizer-BioNTech vaccine were given a booster dose six months later. Overall, the researchers found that the booster increased antibodies six-fold against the original version of the coronavirus. In addition, an analysis of blood samples from 30 of the children found that the booster generated a 36-fold increase in neutralizing antibodies against the omicron variant. According to the companies, they plan to ask FDA to authorize a booster shot for children ages 5 to 11 in the coming days and will also share the data with other regulators worldwide. Most recently, FDA in January expanded Covid-19 booster eligibility to children ages 12 to 15. However, the World Health Organization has said there is no evidence that healthy children and adolescents need Covid-19 boosters. (Knutson, Axios, 4/14; Neergaard, Associated Press/STAT News, 4/14)