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Adjuvanted trivalent flu vaccine best option for over-65s

Limited benefit using quadrivalent vaccines for elderly as childhood programme cuts flu B circulation

Louise Prime

Tuesday, 30 January 2018

A programme using adjuvanted trivalent vaccine (aTIV) would be a more effective and cost-effective option for vaccinating older people against influenza in the UK, rather than the non-adjuvanted vaccines currently in use for the over-65s, according to Public Health England guidance.

In its summary of the evidence on the choice of influenza vaccination for adults in primary care, PHE reported that there is increasing evidence of the poor performance of non-adjuvanted, standard influenza vaccines in older people. It cited a meta-analysis of data for 2004-15 that did not find any significant efficacy for the inactivated influenza vaccine in the elderly against the A(H3N2) flu virus – the sub-type associated with significant impact in older people, typically resulting in excess mortality and causing outbreaks in often highly vaccinated residents in care homes.

In response to this limited effectiveness, some pharmaceutical companies have been working on vaccines that produce a better immune response in older people, and an aTIV (Fluad) is now licensed in the UK for people of 65 and older. The aTIV has been licensed in some European countries since 1997 and in the US since 2005, and published data show that the adjuvanted vaccine has higher vaccine immunogenicity and higher effectiveness than non-adjuvanted vaccines in the elderly.

PHE’s own mathematical modelling found that: “Even under quite conservative estimates of effectiveness, the adjuvanted vaccine would be highly cost-effective in both the 65-74 and 75 years and over age groups with large reductions in GP consultations and hospitalisations.” It added that the priority for adjuvanted vaccine should be people of 75 and over as they seem to get so little benefit from the standard vaccine.

Quadrivalent influenza vaccines (QIV) cover the two main influenza B strains and aim to improve the breadth of protection provided in seasons when the circulating influenza B strain is not well matched to the single strain contained in the traditional trivalent vaccine (TIV). Because influenza B is relatively more common among children than in older age groups, the main clinical advantage of QIV is in childhood, so influenza vaccines centrally purchased for the childhood programme in recent years have been quadrivalent vaccines.

PHE designed a mathematical model to investigate whether there would also be benefits to using a QIV in adults, as it “offers the potential to provide broader direct protection against influenza B”. This model suggested that, once the UK programme in children of primary school age is fully established, there is still some benefit from using QIV in at-risk adults under 65 years of age, including pregnant women.

However, PHE noted that a successful childhood programme using live attenuated quadrivalent vaccine (LAIV – Fluenz-tetra) is likely to offer indirect protection against influenza B to the whole population, including the over-65s, by reducing the virus’s transmission and circulation. So, on top of the childhood programme, PHE found only ‘relatively small’ additional health benefits of using QIV in older people.

It concluded: “Based on the existing evidence, and in the context of the UK programme, PHE analysis strongly supports the preferential use of adjuvanted trivalent vaccine in older people. Based on current list prices for adjuvanted and standard vaccines, such a programme is likely to be highly cost effective. The JCVI advised that use of aTIV in those aged 65 years and over would be both more effective and cost-effective than the non-adjuvanted vaccines currently in use.”

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