Public Health England has announced that the current flu vaccine has low effectiveness against the main strain of flu which is currently circulating. Due to the time taken to produce enough vaccine stocks, decisions on which flu strains are included in the vaccine each year are made months in advance of the flu season.
Dr Marc Baguelin, Mathematical Modeller and Health Economist, Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, said:
“One key component of the design of the UK selective immunization programme against influenza has been to look at its long-term effect. For this, the benefit of the vaccine in terms of protection provided to the population over several seasons is compared against the cost of this vaccine. In the long term, it has been shown to be highly cost-effective. This means that the benefits (in term of reducing influenza episodes, hospitalisations and deaths in the UK population) exceed greatly the cost of the vaccine. This remains true in the long term, despite some seasons (like this one) presenting low activity or poor match of one vaccine strain compared to the circulating strains.
“Given the unpredictable nature of influenza virus dynamics, flu vaccination is the best intervention we have at the moment to prevent deaths and hospitalisations through direct or indirect protection. Additionally, vaccines usually aim at providing protection against three or four different strains, so, even in a year where there is a mismatch between one of the vaccine strains and one of the circulating strains, the vaccine still gives protection against the other strains.”
Dr Tarit Mukhopadhyay, Lecturer in Vaccine Bioprocess Development, UCL, said:
“Taking the flu jab wasn’t a waste as it protects from 3-4 of the most common circulating strains and while one of the strains is mismatched, it does protect against the other strains.
“With remedial measures, such as antivirals, it is unclear as to how effective it would be against the H3N2 strain that is mismatched. Though having said that, if you’re in a risk group and have breathing difficulties then report it to your healthcare provider.
“It is unfortunate that this has happened, but I don’t there is anyone to blame. The WHO and other scientists are required to predict what the circulating strains are around 8 months in advance of the flu season and that is when manufacturer of the vaccine begins. Normally they get it right, but occasionally a mismatch can occur. But because of the lead times involved with the manufacture of the flu jab, changing strains late on is extremely difficult.”
Dr Michael Skinner, Reader in Virology and Head of the Vaccine Vector Group, Imperial College London, said:
“Even from the perspective of someone like myself who has some interest in helping develop newer and better types of influenza vaccine, the current type of seasonal influenza vaccine is, at the moment, the best we have. Annually it saves tens of thousands of lives. Unusually, but not uniquely, this year one (H3N2) of the four targeted viruses “drifted” (mutated) in an unanticipated direction after the vaccine was formulated for production, so that the vaccine offers little protection against the drifted H3N2. Even so, the vaccine still protects against the other three components (pre- and post-2009 H1N1 and B). And it does at least stop the virus drifting back along the path that had been predicted. To describe it as “useless” would be misguided.
“Trying to predict which seasonal flu vaccine to produce each year must be a bit like a Jack Bauer car chase in Los Angeles. At any intersection, the fugitive has three choices of direction. Bauer can’t catch up, and he doesn’t know the ultimate destination, so he has to try to guess the likeliest turns and place his limited team in side streets where they’re most likely to block the fugitive, to slow him down or capture him. Even with Jack Bauer’s experience, this is bound to prove somewhat hit & miss. What Jack really needs is to be able to deploy the national guard to block every side street and drive the fugitive towards the roadblock awaiting him.
“That’s the vaccine we need, one that will work against at least all variants of any one strain (be it H3N2, H1N1, B or even H5N1 or H7N9 should they gain the ability to transmit amongst humans). We’re not particularly close to that goal but (as with HIV) many of the brightest minds in virology, immunology, structural biology and vaccinology are working hard on it. It’s painstaking work, in basic and applied science, and the eventual solution may involve a ‘eureka’ moment from an unanticipated direction but recent developments in vaccines against foot-and-mouth disease virus and respiratory syncytial virus (infantile croup) show that we can make progress against even recalcitrant enemies.”
Dr John McCauley, Director of the WHO Collaborating Centre for Reference and Research on Influenza, MRC National Institute for Medical Research (NIMR), said:
“The viruses that cause human influenza each year come in three varieties, influenza A(H1N1), influenza A(H3N2) and influenza B viruses. Influenza vaccines are designed to give protection against each of these three viruses. The vaccines take several months to prepare and so the recommendations for which particular strains of virus are to be used for the Northern Hemisphere influenza vaccine campaign, for vaccines given in October and November in advance of the influenza season, are defined in February each year, with approval by the regulatory agencies (e.g. the European Medicines Agency) one or two weeks later. On 20th February 2014 WHO announced the recommended composition of influenza virus vaccines for use in the 2014 – 2015 Northern Hemisphere influenza season. At that time the predominating influenza A(H3N2) was similar to the virus circulating the previous year.
“However the influenza A(H3N2) viruses circulating in many countries of the world in early 2015 are antigenically different from the H3N2 virus that predominated during the influenza season last year. This newly emerged virus was first detected by the WHO Global Influenza Surveillance and Response System, a network of 142 laboratories in 112 countries around the world in late-March 2014, too late to be included in the vaccine. Indeed, even through the summer months it was uncertain whether this new antigenically variant virus would predominate in the Northern Hemisphere winter (2014 – 2015) influenza season.
“The vaccine is expected to give good protection against two of the three viruses responsible for influenza but the emergence of this antigenically variant virus during the year shows how difficult it can be to always have the best influenza vaccine possible. Nevertheless, vaccination is still recommended for people in at-risk groups and pregnant women.”
Dr Tarit Mukhopadhyay is funded by the EU on a project working on a Universal Flu Vaccine.
Dr Michael A. (Mike) Skinner is a Reader in Virology at Imperial College London and Head of the Vaccine Vector Group. He receives research funding from the BBSRC to study host innate responses and recombinant vaccine vectors. He is Chair of the HSE’s Scientific Advisory Committee on Genetic Modification (Contained Use). He is also member elect of the Council and governing trustee of the Society for General Microbiology.Commercial conflicts of interest – none.
Dr John McCauley is Director of the WHO Collaborating Centre for Reference and Research on Influenza at the MRC National Institute for Medical Research. His work is funded by the Medical Research Council.