News Scan for Sep 02, 2020

Fading measles immunity over time
Few global flu detections
Avian flu in Russia, Taiwan

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

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