It's the month of June and in the world of health, thoughts are shifting to sun block, heat wave preparations and travel vaccines. Winter vaccinations seem far off but it may surprise you that your flu vaccine preparations for this coming winter should have started in February of this year. That is the time to get your vaccine orders in for the next season and to take part in or undertake your own ‘wash up’, looking at what worked well this past season, what didn't and horizon scanning for what may be coming (for example changes in your population or new vaccines).
Flu season 23/24
Since the flu pandemic of 2009 (with exception of the two pandemic years), our ‘flu seasons tended to have followed a low and late pattern. By this I mean influenza starts circulating around January with type A strains first then followed by type B leading into April and May. The season 2017/18 was marked by high excess deaths due to flu (you may remember this as the time of the ‘Australian’ and ‘Japanese’ Flu reported in the media when type A(H3N2) mutated and type B Yamagata strain was prominent). The season 2022/23 was another exception to the trend. Influenza started circulating relatively early in the winter but peaked quickly. Hospitalisations across all ages were higher than average and there was a huge increase in excess deaths, with 2022/23 having higher number of deaths associated with ‘flu infection (14,500) than the average figure (13,500) for the 5 years before the COVID-19 pandemic (UKHSA 2023). The reasons for this are multi-fold, but type A (H3N2) was the dominant sub-type that year and this is known to be more severe in the older age groups. There was also evidence that there was lower population immunity due to the reduced ‘flu circulation during the pandemic thanks to social distancing and other non pharmaceutical measures. This meant the population were more susceptible to flu, although there the vaccines were well-matched with the strains that year.
The pattern of influenza was different in 2023/24. Reported positivity rates were considerably lower than 2022/23 (and compared to 2017/18 onwards). Rates peaked in January but as of week 18, remain higher than 2022/23 and follow that low late pattern (UKHSA 2024). There were other respiratory infections in circulation like COVID-19, adenovirus, RSV and rhinovirus and with a rise in whopping cough cases this past winter, it may feel like we had a winter of lots of ‘flu like symptoms. A question that gets asked quite a bit is whether the low influenza level could lead to compliancy in having the ‘flu vaccine. This past 23/24 season has seen a drop in national uptake levels of the ‘flu vaccine. Almost 78% of the over 65s received a vaccine, 41.4% of clinically at risk, 32.1% of pregnant women and 44.1% of all 2 year olds and 44.6% of all 3 year olds (UKHSA 2024b) These rates are down from the uptake rates in 22/23 – e.g. almost 80% of over 65s received a vaccine in 22/23. Our flu vaccine rates do fluctuate over the years and ‘flu vaccine can be a victim of its own success – greater uptake of vaccine, lower the level of virus circulation. However, influenza isn't going away and there is always the threat of a new shift in one of the type A viruses, bringing about a whole new pandemic. ‘Flu vaccine is given to those individuals who are at most risk of serious disease if infected with influenza. It is important that those individuals are annually offered and receive vaccination irrespective of whether circulation of influenza is high or low. It's about their personal protection.
Disappearance of one of the Type B strains
There are two sub-types of Type B influenza – B/Yamagata and B/Victoria. Since the pandemic of 2020, there has been an absence of confirmed detection of naturally occurring B/Yamagata lineage viruses. As a result, the WHO influenza vaccine composition advisory committee recommended that we no longer include B/Yamagata in the quadrivalent influenza vaccine as B/Yamagata is no longer a risk to public health (ECDC 2024) This has led to the EU adapting trivalent vaccines for 2024/25 (EMA 2024). However, in the UK the Joint Committee for Vaccines and Immunisations (JCVI) review the evidence for vaccines and have continued to recommend the quadrivalent vaccines for the UK population (DHSC 2024).
Changes to timing of vaccines
It has become typical practice across many general practices to vaccinate the over 65s as soon as possible in September. However, there has been evidence that since this cohort experiences immunosenescence, antibodies prompted by the ‘flu vaccine can wane by the time the ‘flu season is at its peak in December/January. The closer vaccination is given to ‘flu season, the better the vaccine effectiveness would be during the period of peak influenza activity. During the 2022/23 season, significant waning of vaccine effectiveness for type A strains in adults 18-64 years and in over 65s. There was no waning in children. This despite usage of the newer adjuvanted and cell based quadrivalent vaccines, prompting the JCVI to reconsider the timing of vaccine delivery (JCVI 2024).
This year's National Immunisation Programme Letter outlines changes to timing of vaccines moving the start of the programme for most adults to the beginning of October. This is on the understanding that the majority of the vaccinations will be completed by the end of November, closer to the time that the flu season commonly starts. As flu circulation in children normally precedes that in adults, the children's programme should continue to start in September as early as delivery and supply allows (DHSC 2024). Vaccinating children early is also important as there is indirect protection from the child vaccine (children are the superspreaders of influenza). There are no changes to the maternal programme. Pregnant women can start receiving the vaccine from 1st September and should be offered it up to March 31st each year. The low uptake of ‘flu vaccine amongst pregnant women is a concern as vaccination is needed to protect the woman, her unborn baby and the first few months of the infant's life.
Final thoughts
Key to good vaccine uptake is the preparation. Down through the years, my experience of the practices with the highest uptake were those that were most prepared. When ‘flu season started, they started well and finished well (the gap in uptake between practices who go on to meet the target and those who do not appears early in the season –i.e. practices who achieve the target, vaccinate more volume in the first 7 weeks). Also key to improving ‘flu vaccination uptake is increasing demand and access to ‘flu vaccinations. Community pharmacy in particular, are well placed to help improve flu vaccine coverage, including having the time to talk to patients about any concerns or information they may need about the vaccines. Patient invite/reminder systems, roving models and ‘flu vaccine clinics also can help improve uptake.