#12,875
While there have been increasing hints throughout the year, over the past 30 days we've seen a string of reports indicating that the level of protection provided by last year's flu shot - specifically against the H3N2 virus - was modest for adults under the age of 65, and declined sharply among those older.
Eurosurveillance: Low H3N2 Vaccine Effectiveness In Australia's 2017 Flu Season
Eurosurveillance: Low 2016/17 Vaccine Effectiveness (VE) Among Elderly Hospitalized H3N2 CasesThis is of particular concern because:
ECDC: H3N2 Flu Vaccine Component Likely `Suboptimal'
- This year's Northern Hemisphere flu shot carries forward the same H3N2 vaccine strain
- H3N2 is expected to once again be the dominant flu strain this year
- And those over 65 are typically hardest hit by H3N2 influenza
While that might not seem like much, getting the flu vaccine this year could still mean the difference between having a nasty flu, and a life-threatening one.As we've seen repeatedly over the past few months (see The Enigmatic, Problematic H3N2 Influenza Virus), coming up with a good vaccine match for seasonal H3N2 has become increasingly difficult due to increased viral diversity, and mutations that can crop up during the (primarily egg-based) manufacturing process.
While the WHO announced a strain change for next year's Southern Hemisphere flu shot a little over a month ago (see WHO: Recommended Composition of The 2018 Southern Hemisphere Flu Vaccine), that won't roll off the manufacturing lines until next spring, and won't be a factor in this year's flu season.
Today's Eurosurveillance Journal has a detailed end-of-season report on last year's flu Vaccine Effectiveness (VE), broken down by age groups, and by flu strain. Unlike here in the US, they continued to allow the use of a live attenuated nasal spray vaccine (LAIV), along with the traditional inactivated flu jab (IIV).
H1N1 wasn't a factor last year, and the VE against influenza B ranged from 52.1% in adults (age 18-64) to 78.6% in children who received the LAIV4 vaccine.The performance against H3N2 in adults aged 18–64 averaged a modest 36.6% - roughly equivalent to what was reported in the US last winter - but dropped precipitously for those over 65 with their analysis showing `no significant effectiveness against influenza A or specifically A(H3N2) in those aged 65 years and above (aVE: -68.4%; 95% CI: -248.9 to 18.7).'
Also addressed in this report is the ongoing controversy over studies from the United States showing reduced protection (primarily against H1N1) in recipients of the LAIV vaccine two years ago, which led the temporary suspension of the nasal spray vaccine here in the US.
They call this past year's performance against H3N2 `reassuring', but say it will `. . . be critical to continue to monitor the effectiveness of LAIV in the forthcoming season', particularly with the recent strain change to the new A/Michigan/45/2015 (H1N1)pdm09-like virus.Follow the link below to read the full, data-rich analysis. I've only included some excerpts (emphasis mine).
End-of-season influenza vaccine effectiveness in adults and children, United Kingdom, 2016/17
Richard Pebody1, Fiona Warburton1, Joanna Ellis1, Nick Andrews1, Alison Potts2, Simon Cottrell3, Arlene Reynolds2, Rory Gunson4, Catherine Thompson1, Monica Galiano1, Chris Robertson5, Naomh Gallagher6, Mary Sinnathamby1, Ivelina Yonova7,8, Ana Correa7, Catherine Moore3, Muhammad Sartaj6, Simon de Lusignan7,8, Jim McMenamin2, Maria Zambon1
Introduction
The United Kingdom (UK) has a long-standing influenza selective immunisation programme offering inactivated vaccine to people 65 years of age and older and those 6 months to less than 65 years of age with an underlying clinical risk factor [1]. Following advice from the Joint Committee on Vaccination and Immunisation (JCVI), the UK started the incremental introduction of a universal childhood influenza vaccine programme in the 2013/14 influenza season [2] with a newly licensed intra-nasally administered live attenuated influenza vaccine (LAIV).
(SNIP)
The 2016/17 influenza season in the UK, as with many other northern hemisphere countries, was characterised by the early circulation of influenza A(H3N2) viruses. The season started in December 2016 and peaked over the Christmas/New Year period. It was characterised by large numbers of care home outbreaks, many of which included highly vaccinated populations, increased admissions to hospital compared with the previous season and significant excess mortality particularly among those 65-year-old or older, despite vaccine uptake levels of over 70% in this age group [6].
Questions have been previously raised about the effectiveness of inactivated influenza vaccine in older persons and a range of potential explanatory factors have been postulated including what role prior vaccine exposure may play in reducing VE in this age group [7].
The UK has a well-established system to monitor influenza VE each season, including mid-season estimates based upon sentinel swabbing in primary care [3,8]. Here we present the 2016/17 end-of-season VE findings for laboratory-confirmed infection in primary care across all age groups, with a particular focus on LAIV4 in children and inactivated influenza vaccine (IIV) in adult age groups and we explore the possible effect of prior season vaccination on VE in the current season. A comparison with the mid-season estimate is also undertaken.
(SNIP)
Vaccine effectiveness against influenza A(H3N2)
In adultsTable 5 shows the age-specific crude and aVE by sub-type. The VE point estimate for inactivated vaccine (IIV) in 18–64-year-olds for influenza A(H3N2) was 36.6% (95% CI: 10.4 to 55.1), however, there was no significant effectiveness against influenza A or specifically A(H3N2) in those aged 65 years and above (aVE: -68.4%; 95% CI: -248.9 to 18.7).
Although further analysis found no statistically significant decline in effectiveness by age in ≥ 18-year-olds (p = 0.516 for linear trend on log-odds), the direction of the trend was towards a decrease in VE with age and this was more rapid in those aged ≥ 65 years.
(SNIP)
We found no evidence of significant negative interference in adults from prior season’s influenza vaccine, although VE was lower among those also vaccinated the previous season. However, the antigenic distance between the A(H3N2) viruses in the current and prior season and between the current season vaccine and current epidemic strain was only small [7].
Our findings do highlight that better vaccines for older adults are required. Adjuvanted vaccines have recently been licenced in the UK, with both them and high dose vaccines available elsewhere in Europe and North America. It will of course be important to determine the effectiveness of these vaccines; early results from the US in elderly people for high dose vaccines have been encouraging [21].
In the meantime, the VE findings for the current generation of inactivated vaccines reinforce the importance of physicians considering the added value of influenza antiviral treatment and prophylaxis for those aged 65 years and older particularly in seasons dominated by A(H3N2).
(SNIP)
In summary, we provide encouraging results for the new UK childhood influenza vaccine programme using LAIV4, albeit in a season dominated by A(H3N2) no significant effectiveness of IIV was demonstrated in adults aged 65 years and above. The level of LAIV4 effectiveness observed in 2016/17 combined with uptake in children [6] should maximise the population level benefits of the programme. These benefits are projected to provide direct protection to those vaccinated, and by reducing children’s rates of infection, to indirectly protect more vulnerable members of their families and communities, in particular older adults and those who belong to a clinical at risk group [28,29].
The findings in both children and those aged 65 years and above will need further epidemiological and virological investigation. Particularly for the former age group, the results from a season dominated by circulation of influenza A(H1N1)pdm09 viruses will be critically important to provide on-going assurance of the optimal design of the UK programme.(Continue . .. )
