For decades, WHO has continued the surveillance of influenza viruses across the globe involving several generations of world-renowned influenza scientists to where it is currently. Yet, influenza continues to remain a threat to humans killing around 650,000 every year. The global influenza surveillance system monitors the changes of the influenza viruses with a combined effort to develop effective seasonal influenza vaccine and powerful antiviral drugs. As the influenza virus continues to change, therefore the composition of the vaccine also requires to be modified to match the circulating influenza viruses of the season. For the selection of vaccine viruses, WHO organizes twice a year consultations with experts from WHO Collaborating Centers (CCs), Essential Regulatory Laboratories (ERLs) along with other partners to review the information gathered by WHO Global Influenza Surveillance and Response System (GISRS) to make the recommendations on influenza vaccine composition for the next influenza seasons.

“What’s unique about influenza is it is constantly changing. So for seasonal viruses, these viruses continue to evolve and change and escape the ability of existing vaccines to protect the population,” said Dr Jacqueline Katz, Director of the WHO Collaborating Centre for the Surveillance, Epidemiology and Control of Influenza, Atlanta, USA. “We’re really concerned about being ahead of the game for detecting a virus that could cause the next global pandemic.”

In order to reduce the rate of mortality associated with influenza, WHO recommends appropriate measures for the prevention, the treatment of the infection and also providing a strategic action plan for pandemic influenza. Here we discuss the WHO recommendations of antiviral treatment, recommended compositions for the influenza vaccines for the northern hemisphere, southern hemisphere, the tropics and the subtropics for the current influenza season.

Guidance on Clinical Management of Influenza

WHO is currently working on developing a standard guideline for the management of influenza infection which will be applicable to all groups of people internationally. However, WHO guidelines for Pharmacological Management of Influenza viruses were revised in 2010 which recommends;

  • Both the high-risk groups and those with severe or progressive clinical presentation

should be treated with oseltamivir or zanamivir as soon as possible.

  • For individuals with severe immunosuppression, higher doses and longer treatment duration should be considered with oseltamivir.
  • In the case of influenza viruses known or suspected oseltamivir resistant, for patients of all groups, the treatment should be initiated with zanamivir as soon as possible.

 

WHO recommended composition of influenza virus vaccines for the northern hemisphere influenza season 2018-2019

For the 2017-2018 influenza season, the viruses activity has been reported in all regions between September 2017 and January 2018. The predominant influenza viruses have been influenza A(H1N1), A(H3N2) and influenza B viruses co-circulating. The influenza activity started early from November in North America and the predominantly identified virus as influenza A(H3N2). There have been reports of very high levels of influenza-like illness and mortality rate in the United States of America in comparison to the recent seasons. For detailed information about the extent and type of influenza activity affecting different countries, visit: http://www.who.int/influenza/resources/charts/en/

The recommended quadrivalent vaccines for the use in 2018-2019 influenza season should contain;

  • an A/Michigan/45/2015 (H1N1)pdm09-like virus
  • an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus
  • a B/Phuket/3073/2013-like virus(B/Yamagata/16/88 lineage)

The recommended influenza B virus component of trivalent vaccines be a B/Colorado/06/2017-like virus of the B/Victoria/2/87-lineage.

WHO recommended composition of influenza virus vaccines for the southern hemisphere influenza season 2018

It is reported that in the Southern hemisphere, the influenza activity was identified between the months of February and September 2017 with the predominance of influenza A (H3N2) and influenza B viruses. In southern Africa the influenza activity was reported from June to August and most countries in the southern cone of the Americas, the high levels of activity was reported from August onwards.

For the 2018 season in the southern hemisphere, the WHO recommended trivalent vaccines should contain;

  • an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus;
  • an A/Michigan/45/2015 (H1N1)pdm09-like virus and
  • a B/Phuket/3073/2013-like virus

The quadrivalent vaccines should have two influenza B viruses and have the above three viruses and a B/Brisbane/60/2008-like virus.

 

Influenza Vaccine in Tropics and Subtropics

The countries of the tropics and subtropics have over the last decade been interested in the expansion of seasonal influenza vaccination as part of their national immunization program. Because of the complexities involved such as year round activity of influenza in the tropics and subtropics, the two challenges occurred; which formulation to use and when to vaccinate for these countries. Therefore, WHO Global Influenza Program recommends that an evidence-based practical approach should be used for countries presenting same seasonality and virus antigenic characteristics. Accordingly, the countries are assigned to two categories; countries with primary influenza activity beginning after October and the countries where the activity begins after April.

A third recommendation for vaccine composition for the tropics and subtropics are not required as from the antigenic evolution perspective, there has been no evidence to suggest the need for it. Therefore, according to WHO, the most recent influenza virus vaccines are recommended, based on the independent hemisphere the country is located.

WHO Strategic Action Plan for Pandemic Influenza

Now that we are 100 years after the 1918 Influenza Pandemic that killed millions of people around the globe, the influenza viruses still continue to be a threat to humans. As the pandemic outbreaks have been unpredictable in history, therefore preparing for the next pandemic is very important.  The new strategy of WHO will help build greater global preparedness in the event of another pandemic by providing improved influenza forecasting and the development of a possible universal influenza vaccine. The Global Influenza Surveillance and Response System (GISRS) and the Pandemic Influenza Preparedness Framework help developing countries so they can access vaccines, antiviral drugs and prepare for the management of pandemics.

References

http://www.who.int/influenza/spotlight

https://www.who.int/influenza/vaccines/virus/en/

http://www.who.int/influenza/vaccines/tropics/vaccination_formulation/en/

http://www.who.int/influenza/vaccines/virus/recommendations/201802_recommendation.pdf?ua=1

http://www.who.int/influenza/vaccines/virus/recommendations/201709_recommendation.pdf?ua=1

http://www.who.int/influenza/surveillance_monitoring/updates/2018_10_14_influenza_update_326.jpg?ua=1

http://www.who.int/influenza/pandemic-influenza-an-evolving-challenge/en/

https://www.who.int/csr/resources/publications/swineflu/h1n1_guidelines_pharmaceutical_mngt.pdf?ua=1