Monday, September 21, 2020

WHO Convenes On Southern Hemisphere Flu Vaccine & Cambodia Reports Outbreaks Of H3N2

Flu Reports Flat-lined Since Late March - Credit WHO


Late last week in WHO Influenza Update #376 & MMWR: Decreased Influenza Activity During COVID-19 Pandemicwe looked a the dearth of flu reports from around the world since last spring - beginning shortly after the Coronavirus pandemic took hold - and some of the challenges that could arise over the next 12 months from this lack of data. 

While this fall's northern hemisphere flu vaccine is already produced and largely delivered, decisions are expected to be made later this week on next year's (2021s) Southern Hemisphere flu vaccine. 

Normally those decisions are guided by the data collected between March and September, of which there is currently precious little (see ECDC: Influenza Virus Characterisation - Summary Europe, July 2020).  

What little data we have seen over the past few months suggests increasing diversity among H1N1 viruses, a continued chaotic H3N2 landscape, and the dominance of the Victoria lineage among Influenza B viruses.  

This week, the WHO will convene a meeting of flu experts from around the world to decide on what vaccine strains to include in next year's flu vaccine.  Given the limited amount of flu data available, this year's vaccine component decisions are going to be more difficult than normal. 

WHO Consultation and Information Meeting on the Composition of Influenza Virus Vaccines for Use in the 2021 Southern Hemisphere Influenza Season

WHO e-Consultation

16 September - 02 October 2020

(16 - 24 September on seasonal influenza; 29 September - 02 October on influenza of pandemic potential)


The periodic review and update of viruses contained in influenza vaccines is necessary in order for the vaccines to be effective due to the constant evolving nature of influenza viruses, especially those circulating and infecting humans.

Twice annually, WHO organizes consultations with an advisory group of experts to analyse influenza virus surveillance data generated by the WHO Global Influenza Surveillance and Response System (GISRS), and issues recommendations on the composition of the influenza vaccines for the following influenza season. These recommendations are used by the national vaccine regulatory agencies and the pharmaceutical companies to develop, produce and license influenza vaccines.


  • Analyse the antigenic and genetic characteristics of seasonal influenza viruses circulating and infecting humans, taking into consideration the available epidemiological and clinical information from individual countries and regions;
  • Make recommendations on the composition of influenza virus vaccines for use in the 2021 southern hemisphere influenza season; and
  • Review the antigenic and genetic characteristics of recent A(H5), A(H7), A(H9), and other subtype or variant influenza viruses infecting humans recently, and the need to develop new candidate vaccine viruses for pandemic preparedness purposes.

Participants (by invitation)

  1. Representatives from WHO Collaborating Centres for influenza (CCs) of GISRS;
  2. Representatives from WHO Essential Regulatory Laboratories (ERLs) of GISRS;
  3. Representatives from National Influenza Centres and WHO H5 Reference Laboratories of GISRS;
  4. Representatives from the WHO Collaborating Centre for Modelling, Evolution, and Control of Emerging Infectious Diseases; and
  5. Representatives from the OIE/FAO Network of expertise on animal influenza (OFFLU), and other experts.

Provisional main agenda items

  • Review of antigenic and genetic characterization data of seasonal, zoonotic and relevant animal influenza viruses analysed by CCs and other reference laboratories;
  • Review of the global influenza activity;
  • Analysis of results of vaccine serological studies;
  • Recommendations for the composition of influenza virus vaccines for use in the 2021 southern hemisphere influenza season;
  • Review of the need and subsequent selection of new A(H7N9), A(H5) and other subtype or variant viruses for the development of new candidate vaccine viruses for pandemic preparedness purposes.

Publication date: 31/08/2020 

Although the WHO has received a smattering of flu samples over the summer (see WHO Influenza Update #376), it has been at a rate of less than 1/100th of normal.  The WHO Flu activity map (below) has remained mostly blank all summer. 

Influenza has been a no-show for pretty much the last 6 months, but over the weekend we are suddenly seeing reports out of Cambodia - via the Vietnamese press - of a multi-province outbreak of influenza H3N2. 

While normally this would be a fairly insignificant report, against a backdrop of practically no flu reports since the spring, this is getting a lot of attention in neighboring Vietnam.  

This report from 

In the eight provinces where influenza A H3N2 occurs in Cambodia, there are 3 provinces bordering Vietnam: Takeo, Tbong Khmum and Rattanakiri.
Nguyen Vu Hung (VNA / Vietnam +) 20/09/2020 17:53 GMT + 7

On September 19, the Ministry of Health of Cambodia reported the outbreak of influenza A H3N2 in 8/25 provinces of this country.

According to a Vietnam News Agency reporter in Phnom Penh, as of the morning of September 19, more than 570 people were infected with the H3N2 virus, mainly monks at temples in the provinces of Takeo, Battambang, Tbong Khmum, Bantey Meanchey and inmates in Preah provinces. Vihear, Koh Kong, Kampong Thum.

Currently, 100% of patients in 7 provinces have recovered from the disease, but only 15% of patients in Kampong Thum province have recovered from the disease.

Of the eight provinces where influenza A H3N2 occurs, there are 3 provinces bordering Vietnam: Takeo, Tbong Khmum and Rattanakiri.

Research results of the Ministry of Health of Cambodia showed that all of the above patients did not have acute respiratory infections COVID-19.

          (Continue . . . )


Although this is the first flu outbreak we've seen reported in months, there is nothing (at this time) to suggest there is anything unusual about this H3N2 outbreak.  

With large gaps in recent flu surveillance, however, it would be nice to have an antigenic analysis of this virus, to see what - if anything - has changed with this subtype since last winter. 

H3N2 is generally associated with harsher flu seasons - particularly for the elderly - and its been more than 2 years since the last H3N2 dominant season (2017-2018), which saw an estimated 61,000 influenza-associated deaths in the United States.

While one outbreak certainly can't tell us what kind of flu season lies ahead, we'll be watching other nations in the region to see if they start reporting an uptick in flu activity as well. 

Stay tuned.