Seasonal Influenza is caused by a number of circulating Influenza viruses such as Influenza A HINI, H3N2, Influenza B etc. While declaring the Pandemic to be over in August 2010, World Health Organization conveyed that Pandemic Influenza A (HINI) virus that caused Pandemic (2009-2010) would circulate as Seasonal Influenza virus and would continue to do so for years to come.
Seasonal Influenza may affect all age groups; globally incidence is higher in young children and those above 65 years. Health workers and persons with comorbid conditions (such as lung disease, heart disease, liver disease, kidney disease, blood disorders, Diabetes) and immuno-compromised persons are at higher risk. Influenza may have an aggressive course in extremes of age and in co-morbid conditions.
World Health Organization recommends vaccination of high risk groups with Seasonal Influenza Vaccine. Vaccination is an important tool to prevent infection and severe outcomes caused by influenza viruses. Over the years, evidence has been established through research globally on the protection provided by Seasonal Influenza Vaccine, in particular for those at higher risk. It helps protect women during pregnancy and their babies up to six months and among vaccinated, reduction in influenza related hospitalizations across all age groups is expected.
In India, available information suggests that in the post pandemic period (2012-2015) Seasonal Influenza has affected persons mainly in all age groups. Analysis of mortality of laboratory confirmed cases suggest that about 50 % of those affected had co-morbid conditions.
Based on epidemiological evidence, the advice received from World Health Organization, Indian Council of Medical Research and subject experts, Government of India recommends vaccination of High Risk Groups with Seasonal Influenza Vaccine. The recommendations for prioritized groups are as under:
Seasonal Influenza Vaccine recommended for the season of 2019-20
Indian Council of Medical Research (ICMR), Government of India has recommended Northern hemisphere Quadrivalent / Tetravalent vaccine (as recommended by WHO) needs to be used.
WHO recommended composition of influenza virus vaccines for use in the 2019-2020 northern hemisphere influenza season is as follows:-
It is recommended that quadrivalent vaccines for use in the 2019-2020 influenza season (NH winter) contain the following:
It is recommended that the influenza B virus component of trivalent vaccines for use in the 2019-2020 northern hemisphere influenza season be a B/Colorado/06/2017-like virus of the B/Victoria/2/87-lineage.
Ministry of Health and Family Welfare recommends the vaccine as detailed mentioned above.
The State Governments/ Union Territory Administration, depending upon the public health burden of Influenza, would evolve a plan for vaccinating the health care workers/ persons at higher risk, on yearly basis. States/UTs may take appropriate steps for undertaking immunization of healthcare workers based on usual timing of disease outbreaks in their State/region. The concerned hospitals would also have an action plan to vaccinate their health care workers on yearly basis.
Influenza vaccination is most effective when circulating viruses are well-matched with vaccine viruses. Even with appropriate matching, efficacy of vaccine may be about 70% to 80%. In case the locally circulating virus is different from vaccine virus recommended by WHO, it may be partially effective or not be effective at all. Hence, vaccine should not give a false sense of security. Considering the risk perspective, the modalities of infection prevention and control practices like personal hygiene, frequent washing of hands, respiratory etiquettes and airborne precautions (in hospital settings or domiciliary care settings) should be strictly adhered to.
The available vaccine takes about 2-3 weeks for development of immunity. Hence for the health care workers working in an environment with likelihood of exposure to Influenza virus, vaccine should be administered at least one month prior to the commencement of the season, till such time use of chemoprophylaxis may be considered.