The RACGP president Dr Bastian Seidel is advising us not to get the flu vaccination too early in the season, as protection during the flu season will be less effective. He made the media announcement in response to many pharmacies this week launching campaigns that encouraged people to get their flu shots as early as possible.
Protection from vaccination is known to reduce over time and recent evidence demonstrated this to be by 6-11% per month and those over 65 years particularly have been shown to lose vaccine-induced immunity at an even faster rate. The flu season is usually between June to September, with a peak in August. The community is strongly advised to have the vaccine closer to the start of the flu season, closer to May.
The vaccine usually provides about a 60% protection from the circulating flu strains during the winter. The flu strains contained in the vaccine are chosen after assessing the circulating strains in the opposite hemisphere winters and the predictions can be poor as a result of the complicated possibilities, the nature of the influenza virus and perhaps the modern ease and frequency of travel across continents by large numbers of people. The vaccine strain can change in the 6 months between being chosen for the next winter and manufacture and distribution. The egg-grown H3N2 vaccine virus strain also changed during vaccine production for the 2017 vaccine in Australia.
There are several flu types circulating every year, the different strains posing different threats to the various age groups in the community. The different strains can be easily distinguished by laboratory tests, but not by clinical symptoms. The types of circulating virus strains are published at the end of winter from national Influenza Centres and data is reported to FluNet internationally. The WHO FluNet Summary provides real-time data on the current global circulation of influenza viruses and the vaccine effectiveness for the past season is also provided. The WHO network provides early detection of new influenza subtypes with the potential to cause a pandemic and monitors antigenic and genetic changes occurring in recently circulating influenza A and B viruses to assist the WHO in formulating the twice yearly recommendations on the most appropriate compositions of influenza vaccines. The information is available on the World Health Organisation website here.
Worldwide, influenza A and influenza B accounted for similar proportions of infections in the northern hemisphere winter of 2018.
The UK season had “Aussie flu”, influenza A ( subtype H3N2) in circulation, particularly causing serious illness and death in the elderly. The vaccine effectiveness was estimated as 39.8% for all ages , but gave no effectiveness in those older than 65 years. The Influenza B, Yamagata lineage was also circulating in similar numbers and caused significant illness in the UK and was not included in the vaccine. Children are most susceptible to the Influenza B viral strains
The Aussie Flu (AH3N2) was most prevalent last season in the USA and also caused most complications in the elderly. The US vaccine all-age effectiveness last winter was 32% for H3N2 and 10% for Influenza B Yamagata.
During the 2017 season, only 27% of all Australians were vaccinated at all, with 6% of children being vaccinated. The vaccine provided 33% protection ( 5-19% for H3N2 and 37% against H1N1 ). There were 1,100 deaths from flu-related causes – 90% were aged 65 years and over. Australia recorded 221,853 flu infections to November 2017, significantly more than other years.
This year two new vaccines are funded and recommended for those over 65 years, hoping to provide better protection than that given to the US and UK populations of over 65 year olds for winter 2018. Both contain 3 strains only for influenza A, not influenza B. The seasonal flu vaccine now contains four strains to cover all the relevant subtypes present, but protection against H3N2 infection appears to be poorer than the other strains. The benefits of better protection against the most common three flu strains appear to outweigh the potential loss of protection against the missing B strain for the elderly.
– Fluzone High Dose ( contains 4 times the flu antigen. This vaccine increases antibody response, particularly against the H3N2 strain which causes more problems for older people, particularly with a complicating pneumonia.
– Fluad, This vaccine contains an adjuvant to boost the immune response. It has been used overseas for some years and observational data indicates less hospitalisations and less pneumonia infections associated.
The new vaccines are not live, do not cause flu and both give more local side-effects such as painful injection sites or fever. There are no head-to-head comparisons of effectiveness and studies suggest similar results.
There is no data to support the use of different doses, nor multiple doses, with the vaccine given at each site most likely to be the one that has been made available to the Clinic.
No vaccine provides guaranteed protection, but reduces the risk of getting flu.
For very detailed information about influenza, the influenzacentre.org website is a useful resource and provides the current vaccine recommendations and surveillance report links available and the Australian Immunisation Guidelines for those who are at increased risk from influenza other than those over 65 years, such as pregnant women, those with lung and chronic diseases and with immunodeficiency states.
Dr Lisa Surman, CBD West Medical Centre, Perth, WA
Member of Best Practice Software’s Clinical Leadership Advisory Committee
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