Vaccine effectiveness against influenza A(H3N2) and B among laboratory‐confirmed, hospitalised older adults, Europe, 2017‐18: A season of B lineage mismatched to the trivalent vaccine

Abstract

Background: Influenza A(H3N2), A(H1N1)pdm09 and B viruses co-circulated in Europe in 2017-18, predominated by influenza B. WHO-recommended, trivalent vaccine components were lineage-mismatched for B. The I-MOVE hospital network measured 2017-18 seasonal influenza vaccine effectiveness (IVE) against influenza A(H3N2) and B among hospitalised patients (≥65 years) in Europe.Methods: Following the same generic protocol for test-negative design, hospital teams in nine countries swabbed patients ≥65 years with recent onset (≤7 days) severe acute respiratory infection (SARI), collecting information on demographics, vaccination status and underlying conditions. Cases were RT-PCR positive for influenza A(H3N2) or B; controls: negative for any influenza. "Vaccinated" patients had SARI onset >14 days after vaccination. We measured pooled IVE against influenza, adjusted for study site, age, sex, onset date and chronic conditions. Results:We included 3483 patients: 376 influenza A(H3N2) and 928 B cases, and 2028 controls. Most (>99%) vaccinated patients received the B lineage-mismatched trivalent vaccine. IVE against influenza A(H3N2) was 24% (95% CI: 2 to 40); 35% (95% CI: 6 to 55) in 65-to 79-year-olds and 14% (95% CI: −22 to 39) in ≥80-year-olds.Against influenza B, IVE was 30% (95% CI: 16 to 41); 37% (95% CI: 19 to 51) in 65-to 79-year-olds and 19% (95% CI: −7 to 38) in ≥80-year-olds. | 303 ROSE Et al.Conclusions: IVE against influenza B was similar to A(H3N2) in hospitalised older adults, despite trivalent vaccine and circulating B lineage mismatch, suggesting some cross-protection. IVE was lower in those ≥80 than 65-79 years. We reinforce the importance of influenza vaccination in older adults as, even with a poorly matched vaccine, it still protects one in three to four of this population from severe influenza. K E Y W O R D SEurope, hospital, influenza, older adults, test-negative design, vaccine effectiveness

Spotlight influenza: Estimation of influenza vaccine effectiveness in elderly people with assessment of residual confounding by negative control outcomes, Finland, 2012/13 to 2019/20

“…In general, the estimated IVE levels are in line with other studies [13][14][15][16][17]. In particular, all these studies indicate that IVE in elderly people usually does not…”

“…In 2017/18, a severe season characterised by co-circulation of influenza A(H3N2) and B/Yamagata viruses, IVE was at its lowest level (16%). Our results and those of a European multi-centre study reveal that the vaccines used in 2017/18 provided better protection against influenza B than against influenza A [ 16 ]. Since those vaccines did not contain virus of the Yamagata lineage, this suggests some degree of cross-lineage protection.…”

“…Influenza vaccine effectiveness against laboratoryconfirmed influenza A and B in people aged 65-100 years, Finland, August 2012-May 2020 [16]. Since those vaccines did not contain virus of the Yamagata lineage, this suggests some degree of cross-lineage protection.…”

COVID‐19 vaccine effectiveness against hospitalization due to SARS‐CoV‐2: A test‐negative design study based on Severe Acute Respiratory Infection (SARI) sentinel surveillance in Spain

“…The test‐negative design has been widely used for influenza VE, among others, within the I‐MOVE network. 41 , 42 Because our study is based on SARI surveillance data, it is likely affected by heterogeneity in data collection of SARI admissions among participating hospitals. These data quality issues are inherent to routine epidemiological surveillance particularly during the first weeks of implementation.…”

Markers of systemic inflammation are positively associated with influenza vaccine antibody responses with a possible role for ILT2(+)CD57(+) NK-cells

“…As observed with SARS-COV-2 [ 9 ], antibody [ 10 ] and cell-mediated [ 11 ] responses to the seasonal influenza vaccine wane with age, as does the effectiveness to prevent hospitalization, although this varies depending on subtype, season, and overall health status [ 12 – 14 ]. Of the three major influenza (sub)types included in the seasonal vaccine, A/H3N2 breakthrough tends to result in more hospitalizations [ 15 ] and mortality [ 16 ] in older adults, partly due to limited vaccine-induced antibody production [ 17 , 18 ], and especially in years of vaccine mismatch [ 19 ].…”