Adjuvanted cell-derived flu vaccine raised titres over the egg-based version in over-50s

Design

Phase 3, randomised, observer-blind, multicentre trial

Population

7,699 healthy adults aged ≥50

Primary outcome

Day-29 haemagglutination inhibition titres and seroconversion

Effect

v aQIV: GMT ratio 1.22–1.73 across strains; v QIVr: H3N2 GMT ratio 0.69 (0.65–0.74), non-inferiority not met

A phase 3, observer-blind trial in The Lancet Infectious Diseases (10 September) randomised 7,699 healthy adults aged 50 or older to one of three quadrivalent vaccines: a new MF59-adjuvanted, cell-derived vaccine with three times the haemagglutinin per strain (aQIVc), the existing MF59-adjuvanted egg-derived vaccine (aQIV), or recombinant vaccine (QIVr).

At day 29, aQIVc produced higher antibody titres than aQIV for all four strains, with geometric mean titre ratios of 1.53 for H1N1, 1.22 for H3N2, 1.73 for B/Victoria and 1.71 for B/Yamagata, and 10–24 percentage points more seroconversion. Against recombinant vaccine it met non-inferiority for H1N1 and both B strains but not H3N2, where titres were lower (ratio 0.69). Local and systemic reactions were more common with aQIVc, mostly mild and short-lived; serious adverse events were 2.8% v 3.5% v 2.9%.

Two cautions. These are antibody levels, not prevented influenza, and H3N2 is the strain that drives much of the severe disease in older adults. The trial was funded by the manufacturer. For now it adds to the case for enhanced vaccines in older adults; whether aQIVc offers more than recombinant vaccine is not shown. Its availability and regulatory status in India are not known.

• For adults over 50, an enhanced (adjuvanted, high-dose or recombinant) influenza vaccine is preferable where available.
• aQIVc beat the older adjuvanted egg-based vaccine on antibody response for all four strains.
• It did not match recombinant vaccine for H3N2, the strain behind much severe disease in older people.
• Warn patients to expect more sore arms and short-lived systemic symptoms with adjuvanted vaccines.

Why it matters

Choosing among enhanced flu vaccines is a real decision each season, and this trial shows the H3N2 gap matters.

Don't overread it

This measured antibody levels, not influenza cases or hospitalisations prevented.

The statistics, in plain English

A geometric mean titre ratio of 1.53 means antibody levels averaged about 50% higher. Non-inferiority means 'not meaningfully worse'; for H3N2 against recombinant vaccine, the ratio of 0.69 fell below the preset margin, so non-inferiority was not shown. Higher antibodies usually mean better protection, but the trial did not count infections.

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