News Scan for Sep 02, 2020

News brief

Waning MMR immunity, vaccine hesitancy, could mean more measles outbreaks

A systematic review and meta-analysis of 62 studies has found that immunity conferred by the measles, mumps, and rubella (MMR) vaccine fades each subsequent year, suggesting that vaccination strategies should be revisited.

The study, published yesterday in The Lancet Infectious Diseases, showed that 96.0% of patients inoculated with the two-dose trivalent MMR vaccine initially developed antibodies against measles, while 93.3% had antibodies against mumps when excluding the Rubini strain (91.1% when including it), and 98.3% produced protective antibodies against rubella. But that immunity lessened each year.

The decreases in immunity could help explain continued measles outbreaks even in countries with high vaccine coverage, the authors said.

"Our meta-analysis provides estimates of primary and secondary vaccine failure, which are essential to improve the accuracy of mathematical and statistical modelling to understand and predict the occurrence of future measles, mumps, and rubella outbreaks in countries with high vaccine uptake," they wrote.

In a commentary in the same journal, Sara Boccalini, PhD, and Angela Bechini, PhD, of the University of Florence in Italy, said that continuing to administer the MMR vaccine is crucial, but it's important to remember that primary and secondary vaccine failure can still occur.

The study authors' models will help public health experts identify the groups most vulnerable to infection, who may already have lower antibody responses, and inform future vaccination strategies to eliminate measles, Boccalini and Bechini said. They added that wild-type viruses and natural vaccine boosters stop circulating when universal vaccination is implemented, which could exacerbate waning immunity.

In addition, vaccine hesitancy has led to lower MMR vaccine uptake in the past 10 years, and a further drop is anticipated owing to COVID-19, meaning that vaccine-preventable diseases could well rise.

"Because of the aforementioned issues, effective organisation of public health initiatives becomes much more important in each country, to protect susceptible individuals and difficult-to-reach populations," Boccalini and Bechini said. "In particular, health-care workers should ensure that they correctly communicate the effectiveness of the MMR vaccine to the general population."
Sep 1 Lancet Infect Dis study and commentary


WHO: Global testing finding very few flu positives

Very little flu has been detected globally, even though some countries have stepped up testing, likely due to COVID-19 impacts, the World Health Organization (WHO) said today in its most recent update. Though the Southern Hemisphere's flu season typically runs from May through October, the season hasn't started.

Of about 198,000 respiratory specimens tested during the first half of August at labs that are part of the WHO network, only 46 were positive for flu. Of those, 31 (67.4%) were influenza B and 15 (32.6%) were influenza A. Of the subtyped influenza A viruses, all were 2009 H1N1.

A few parts of the world reported sporadic detections, including Caribbean and Central American countries, as well as tropical South America, tropical Africa, South Asia, and Southeastern Asia.
Aug 31 WHO global flu update


Avian flu outbreaks reported in Russian and Taiwanese poultry

Russia yesterday reported several more highly pathogenic H5 avian flu outbreaks in poultry, all in the southwestern part of the country, according to a notification from the World Organization for Animal Health (OIE).

Seventeen more outbreaks were detected, all in backyard and village birds, 15 in Omsk oblast and 2 in Kurgan oblast. The events began from Aug 14 to Aug 24, killing 10,660 of 1,564,447 susceptible birds. Culling and safe disposal are under way.

So far, officials haven't detailed the full subtype. In early August, Russia reported two outbreaks involving H5N8 in backyard and village poultry in Chelyabinsk Oblast, located in the Ural Mountains near the border between Europe and Asia.
Sep 1 OIE report on H5 in Russia

Elsewhere, Taiwan recently reported another outbreak involving highly pathogenic H5N5 avian flu. The virus struck a commercial poultry farm housing native chickens.

The outbreak began at a facility in Yunlin County on Aug 15, killing 240 of 10,972 susceptible bird. The remaining chickens were destroyed to curb the spread of the virus. The country has reported sporadic H5N5 outbreaks since September 2019.
Aug 31 OIE report on H5N5 in Taiwan

COVID-19 Scan for Sep 02, 2020

News brief

US experts recommend who should get COVID-19 vaccine first

Healthcare workers, first responders, and adults with pre-existing conditions that put them at risk for severe symptoms of COVID-19 should be the initial recipients of the first approved vaccine in the United States, according to a framework from the National Academy of Medicine (NAM) published yesterday. Today, NAM will hold a virtual public meeting on the recommendations.

The NAM report offers a detailed approach about how to best prioritize and allocate a COVID-19 vaccine. Even though the virus was discovered only in December of 2019, several countries have produced vaccines that are currently in late-stage clinical trials, and US President Donald Trump has said America could see a vaccine by the end of the year.

But deciding who should first get access to the vaccine is a potential problem, compounded by lessons learned in the early months of the US pandemic on how the virus hits minority communities hardest.

The NAM framework offers four phases of vaccine deployment. In addition to the aforementioned groups, older adults in congregate living are included in phase 1. In phase 2, teachers, school staff, critical risk workers, prisoners, those in homeless shelters and group homes, and older adults not included in phase 1 can be vaccinated. Phase 3 is for children, young adults, and workers in industries with exposure to the virus. Phase 4 includes everyone else.
Sep 1 NAM draft report
Sep 2 NAM public listening session


Chinese bus study highlights airborne spread potential of SARS-CoV-2

A study yesterday in JAMA Internal Medicine on a COVID-19 outbreak among bus passengers attending a Buddhist ceremony in China highlights the potential for airborne spread of SARS-CoV-2, the virus that causes COVID-19.

The study looked at 128 people who took two buses to the outdoor worship event at a Buddhist temple in eastern China on Jan 19. Both buses had an air conditioning system on recirculation mode. The total time of travel to and from the event was 100 minutes. None of the people on bus 1 received a COVID-19 diagnosis, while 24 of 68 (35.3%, including the index patient, who was likely exposed on Jan 17) received a diagnosis of COVID-19 after the event. Among the 172 other people who attended the event, 7 (4.1%) subsequently received a COVID-19 diagnosis, and all described being in close contact with the index patient during the event.

Compared with individuals on bus 1, those on bus 2 had a 34.3% (95% confidence interval [CI], 24.1% to 46.3%) higher risk of getting COVID-19, and were 11.4 (95% CI, 5.1 to 25.4) times more likely to have COVID-19 compared with all other people who attended the worship event.

The researchers were able to identify seats for each passenger on bus 2 and divided the seats into high-risk and low-risk zones according to the distance from the index patient, who was asymptomatic during the bus ride. Comparison of COVID-19 risk in the two zones showed that passengers in the high-risk zone on bus 2 had moderately but non-significantly higher risk of COVID-19 than those in low-risk zones, a finding the authors of the study say suggests airborne spread likely played a role.

"If COVID-19 transmission occurred solely through close contact or respiratory droplets during this outbreak, the risk of COVID-19 would likely be associated with distance from the index patient, and high-risk zones on the bus would have more infected cases," they wrote. "These data suggest that forced, circulating air might play an important role in airborne spread of the virus, and gatherings in enclosed settings with minimal air ventilation should be limited."
Sep 1 JAMA Intern Med abstract


Spray from toilets may have caused COVID-19 transmission in China

A study yesterday in the Annals of Internal Medicine adds to the evidence that feces can play a role in the transmission of SARS-CoV2. The study looked at COVID-19 transmission in a cluster of three families living in a high-rise apartment building in Guangzhou, China.

Nine people in the families, who lived in vertically aligned apartments connected by drainage pipes in the bathrooms, were confirmed to have the virus between Jan 26 and Feb 13. After taking 237 surface and air samples from 11 of the 83 flats in the building, public areas, and building drainage systems, the researchers from the University of Hong Kong deduced that virus-containing fecal aerosols were probably produced in the associated vertical stack during toilet flushing, as all families' master bathrooms were connected via plumbing.

"Both the observed infections and the locations of positive environmental samples are consistent with the vertical spread of virus-laden aerosols via these stacks and vents," the authors said.

In an accompanying commentary,  Michael Gormley, PhD, the director of the Water Academy at Heriot-Watt University writes that the findings "add to the growing body of evidence that wastewater plumbing systems, particularly those in high-rise buildings, deserve closer investigation, both immediately in the context of SARS-CoV-2 and in the long term, because they may be a reservoir for other harmful pathogens."
Sep 2 Ann Intern Med study
Sep 2 Ann Intern Med commentary

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