Mass azithromycin, geographic proximity linked to reduced ocular chlamydia

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The results of a randomized clinical trial in Ethiopia suggest mass azithromycin distribution to wide, contiguous areas may reduce the likelihood of the infection that causes trachoma, researchers reported today in Clinical Infectious Diseases.

In the cluster-randomized trial, 60 Ethiopian communities were randomized to receive mass azithromycin distributions (either annually, biannually, or quarterly) over 12 months and 12 to receive no treatments until after the first year. Mass distribution of a single dose of azithromycin has been shown to reduce the prevalence of ocular chlamydia infection—which causes trachoma—in entire communities but has not resulted in complete elimination because of reinfection.

The aim of the trial was to test the theory that reinfection from nearby untreated communities may be a contributing factor. Most infections occur in children under 10 years old.

After assessing a random sample of children ages 0 to 9 years from treated and untreated communities at baseline and at 12 months, the investigators found that the prevalence of ocular chlamydia in the 60 treated communities fell from 43% (95% confidence interval [CI], 39% to 47%) to 11% (95% CI, 9% to 14%). In the 12 untreated communities, prevalence of ocular chlamydia was 46% (95% CI, 38% to 54%) after 12 months.

Untreated areas as reservoirs

In addition, the post-treatment prevalence of ocular chlamydia was significantly higher in communities that were closer to untreated communities after adjusting for baseline prevalence and the number of mass treatments during the year (odds ratio, 1.12; 95% CI, 1.03 to 1.22 for each 1 kilometer closer to an untreated community).

The study authors speculate that routine travel to untreated areas may present opportunities for infections to be reintroduced to treated communities.

"The study supports the World Health Organization recommendation to use districts as the unit of trachoma treatment because administering mass azithromycin distributions over wide contiguous areas should reduce the impact of untreated areas as reservoirs for ocular chlamydia infections," they concluded. 

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Updated COVID shot doesn't spur strong response to newest strains

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In a new University of Texas Medical Branch study, the updated bivalent (two-strain) mRNA COVID-19 booster marshaled a robust antibody response against the Omicron BA.4/BA.5 subvariants but not against the more recently emerged BA.2.75.2, BQ.1.1, or XBB.1 strains.

The authors of the study, published yesterday in Nature Medicine, noted that the BA.2.75.2, BQ.1.1, and XBB.1 subvariants have additional mutations in the spike protein that may affect vaccine effectiveness.

The researchers analyzed the neutralizing effects of three human serum panels collected from COVID-naïve participants (25 sera) 23 to 94 days after a fourth dose of the original Moderna or Pfizer/BioNTech COVID-19 vaccine, 14 to 32 days after receipt of an updated booster after two to four doses of the original vaccine (29 sera), or 15 to 32 days after an updated booster from previously infected participants (23 sera) who had received two to four doses of the original formulation.

The updated booster triggered a high level of neutralizing antibodies against BA.4/BA.5 14 to 32 days later, but it didn't generate robust neutralization against BA.2.75.2, BQ.1.1, or XBB.1.

mRNA platform supports rapid adaption

The researchers said that as of Nov 19, 2022, BA.2.75.2 and the BA.4/BA.5-derived sublineages BA.4.6, BF.7, BQ.1, and BQ.1.1 accounted for 0.8%, 4.4%, 7.8%, 25.5%, and 24.2% of US COVID-19 infections, respectively. The BA.5-derived substrain XBB.1, first identified in India in August 2022, is spreading quickly in Europe and has been found in the United States.

"BA.2.75.2, BQ.1.1, and XBB.1 exhibit the greatest evasion against vaccine-elicited neutralization, suggesting the potential of these new sublineages to dethrone BA.5 as the dominant lineage in circulation," they wrote. "Individuals with SARS-CoV-2 infection history develop higher and broader neutralization against the current circulating Omicron sublineages after the BA.5-bivalent booster."

The authors said that the findings show that future boosters should match newly emerged variants. "Given the advantage of mRNA vaccine platform that can rapidly adapt to new antigen sequences, the key challenge is to determine the future booster sequence before new variants become prevalent in circulation," they concluded.

High-path avian flu strikes more turkeys in 2 states

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Animal health officials have reported more highly pathogenic avian flu outbreaks at commercial turkey farms in Iowa and South Dakota.

The Iowa Department of Agriculture and Land Stewardship said yesterday that the virus was detected at farms in Cherokee and Sac counties, both in the northwestern part of the state.

In South Dakota, the virus struck two more turkey farms, this time in Charles Mix and Clark counties, according to updates from the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS). The two locations have 58,400 birds combined.

The H5N1 outbreaks in poultry, which began in February, have led to the loss of a record 52.9 million birds.

In related developments, APHIS reported 124 more H5N1 detections in wild birds, raising the total to 4,362 since January. Most of the new confirmations reflect testing in hunter harvested birds from multiple states. However, some involved wild birds found dead in states including California, Florida, Indiana, Mississippi, Oregon, South Dakota, and Tennessee.

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