Trivalent flu vaccine won’t protect against influenza B strain predominantly circulating

BMJ 2018; 360 doi: (Published 05 January 2018) Cite this as: BMJ 2018;360:k78
  1. Jacqui Wise
  1. London

Public Health England has warned that the trivalent flu vaccine most commonly administered in general practice will not protect against the strain of influenza B that appears to be predominately circulating this year. The latest figures show influenza is circulating at higher than seasonally expected levels, with increases in GP consultations and emergency department attendance.1

In the last week of 2017 there were 24 influenza deaths reported across the UK with 48 confirmed in the past three months, according to the latest monitoring figures. The overall GP consultation rate for influenza-like illness increased to 21 per 100 000 population, up from 18.9 in the week to 24 December. This is above the normal of 13.1 per 100 000 for this season. There were also increases in out-of-hours calls for influenza-like illness with rates highest in the 15 to 64 age groups.

Data from the sentinel hospital network from 19 NHS trusts across England showed there were 421 hospitalised confirmed influenza cases made up of 179 influenza B cases, 49 A/H1N1, 112 A/H2N2, and 81 influenza A (unknown subtype).

Both influenza A and B are circulating this flu season. Early indications are that viruses related to the B/Yamagata lineage are predominating among laboratory confirmed cases. Out of 25 influenza B viruses analysed by Public Health England’s respiratory virus unit, 21 were the B/Yamagata strain. This year’s trivalent vaccine does not protect against this strain whereas the quadrivalent vaccine, including the nasal spray given to children, provides protection against both strains of B virus.

In a letter sent to GPs in the south-west of England, Mike Wade, deputy director of health protection at Public Health England, said that as most adults will have been vaccinated in general practice with the trivalent vaccine it is possible they will still get flu. It advised doctors that, if there are any patients in at risk groups who have not yet been vaccinated, the quadrivalent vaccine will have the greatest effect given the mixed picture of circulating strains. It added that, in many cases, the trivalent vaccine will still offer better protection than having no vaccine.

Figures from Public Health England found that the influenza vaccination programme in adults aged 18 to 64 reduced the risk of flu by 40.6% in the 2016-17 flu season. However, the flu vaccination programme was ineffective in the over 65s.2 Public Health England has now said that from autumn, in time for the next flu season, GPs should give the adjuvanted flu vaccine, Fluad, to patients over 65. This vaccine has been available in European countries for the past 20 years but has only just been licensed for use in the UK. Until then, however, doctors are advised to keep using the currently available vaccines.

Richard Pebody, acting head of respiratory diseases department at Public Health England, said: “After a comprehensive evidence review, the Joint Committee on Vaccination and Immunisation concluded that this is likely to be cost effective and better at preventing flu in adults over 65 years of age. The committee agreed that over 75s, who generally benefit less from current vaccines, should be considered a priority for receiving the adjuvanted vaccine in 2018-19.”

Pebody added: “At this early stage of the season with influenza just now circulating, there is no evidence yet of significant excess mortality compared with what we would normally see at this time of the year. The current flu vaccine is still the best defence we have. We therefore encourage all those who are eligible to take up the offer of the vaccine.”

On 2 January the National Emergency Pressures Panel said all non-urgent inpatient elective care should be deferred to free up capacity because the NHS has been under sustained pressure over the Christmas period with high levels of respiratory illness and early indications of increasing flu prevalence.3 Chair of the panel, Bruce Keogh, said: “We expect these pressures to continue and there are early signs of increased flu prevalence.”


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