A US study shows that people who had positive home-based COVID-19 test results from January 2021 to March 2022 had a 29% lower likelihood of following isolation recommendations than those with results from a healthcare provider.

Scientists from the Centers for Disease Control and Prevention (CDC) led the panel survey study of COVID-positive people, published yesterday in Emerging Infectious Diseases. In 2021, the CDC recommended that infected people isolate for at least 10 days, shifting to 5 days in 2022.

The CDC estimated that 48,518,190 adults had one or more positive COVID-19 test results; 24% had results from home tests only, and 76% had results from provider tests.

Home tests preclude provider-based education

People with positive home test results had significantly lower odds of isolating for any length of time than those with provider results (78% vs 84%; adjusted odds ratio [aOR], 0.72).

Of patients who isolated, the chances that their isolation met current guidelines were significantly lower among those with home rather than provider tests (64% vs 73%; aOR, 0.71). The adjusted average length of isolation was 2 days shorter among those who used home rather than provider tests.

The authors said that home tests broadened access to COVID-19 diagnosis, particularly for those with no primary healthcare provider or health insurance. But although such tests are convenient and may speed diagnosis, they eliminate the opportunity for providers to offer health education and reinforce the importance of isolation to mitigate COVID spread.

"Clear public health messaging about when and how to test, and the efficacy of each type of test, may help to ensure that persons are testing at the appropriate time," they wrote.

Clear public health messaging about when and how to test, and the efficacy of each type of test, may help to ensure that persons are testing at the appropriate time.

The researchers added that encouraging self-report of positive home test results to health departments would improve COVID-19 surveillance, case investigation, and contact tracing.

"Examining specific individual-level or community-level behavioral factors associated with self-reporting and other public health actions may extend these findings and deepen our understanding of optimal strategies to mitigate future pandemics," they concluded.

Sequential vaccines, like those used for COVID-19, may elicit a greater immune response if the recipient has the same arm injected, called ipsilateral vaccination, as opposed to contralateral vaccination, in which the primary vaccination is delivered in one arm and booster dose is delivered to the opposite. The research is published in EBioMedicine.

German scientists tested immune response and ipsilateral versus contralateral vaccination by looking at data from 303 people who received the Pfizer-BioNTech COVID mRNA vaccine. None participants had not contracted COVID-19 prior to vaccination.

Antibody levels were measured 2 weeks after the second dose in 147 participants who received the second dose of COVID-19 vaccine in the same arm as the first, and 156 who got the second shot in the opposite arm. A subgroup of 143 individuals (64 ipsilateral, 79 contralateral) was analyzed for spike-specific CD4 and CD8 T-cells using flow cytometry, the authors said.

Median spike-specific immunoglobulin levels did not differ between the two groups, but neutralizing activity was significantly lower after contralateral vaccination. The number of cytotoxic CD8+ T cells, known as killer T cells, were detected in 67% of same-arm participants, compared to just 43% of the contralaterally vaccinated subjects.

Our study indicates that ipsilateral vaccinations generate a stronger immune response than contralateral vaccinations.

"Our study indicates that ipsilateral vaccinations generate a stronger immune response than contralateral vaccinations," said researcher Laura Ziegler in a Saarland University press release.

More research needs to be done to confirm these findings, the authors said, but they suggest the effect might be due booster vaccination drainage by the same lymph nodes used for priming.

China has reported three plague cases, involving members of the same family from Inner Mongolia autonomous region, Hong Kong's Centre for Health Protection (CHP) said in a statement today.

A woman, from Xilin Gol Meng, was diagnosed as having plague on August 7, and the infections of her husband and daughter were confirmed on August 12.

Plague is caused by the bacterium Yersinia pestis. The disease is transmitted from infected animals, such as rodents, to humans through flea bites. Other transmission modes include breaks in skin that come in contact with body fluids or tissue of infected animals, consuming infected animal tissue, or inhaling respiratory droplets.

The CHP didn't say how the people contracted their infections of what type of plague they had, but a Reuters report that cited a local government statement said the cases are the more common bubonic type.

• Over the past 2 days, virologists in Israel and Denmark have reported what appears to be a second-generation BA.2 lineage Omicron virus that has numerous mutations in the spike protein, while noting that it's too soon to say what impact it will have and exactly what variant it originated from. T. Ryan Gregory, PhD, an evolutionary biologist who specialized in genomic evolution at the University of Guelph in Canada, said on Twitter that it's notable that the virus isn't restricted to one region. Meanwhile, J. Weiland, an infectious disease modeler, said the yet-unnamed new virus' many spike mutations may come with a wider range of outcomes.
• Finland has announced a plan to test all fur farms for avian flu, which would involve inspections at more than 400 facilities, according to Finnish Broadcasting Corp (YLE). So far, the number of fur farms reporting outbreaks in the country stands at 24. Culling has been ordered at 12 farms, 9 are under surveillance, and 3 are being assessed. Elsewhere, the UK Department for Environment, Food, and Rural Affairs (DEFRA) yesterday published guidance on how to keep pets safe from avian flu, which follows recent detections in cats in Poland and South Korea. The guidance urges people to keep their pets away from dead or sick wild birds, keep them under control in areas where wild birds are located, and avoid feeding pets noncommercial raw poultry meat, game bird, waterfowl, or other wild bird meat.
• The Rhode Island Department of Health today reported a fatal tickborne Powassan virus case, which involved a woman older than 80 years from Washington County, located in the southern region of the state. She experienced neurologic symptoms and died in the middle of July. The Centers for Disease Control and Prevention (CDC) confirmed the findings earlier this month. Powassan virus cases are rare but have increased in recent years. They are most common in the Northeast and Great Lakes regions. Of 239 cases reported over the past decade, 5 were in Rhode Island.