Influenza Vaccine Effectiveness Against Influenza A(H3N2) Hospitalizations in Children in Hong Kong in a Prolonged Season, 2016/2017

Chiu, Susan S.; Kwan, Mike Yat Wah; Feng, Luzhao; Wong, Joshua S C; Leung, Chi‐Wai; Chan, Eunice C.; Chan, Kwok‐Hung; Ng, Tak‐Keung; To, Wing‐Kin; Cowling, Benjamin J.; Peiris, Malik

doi:10.1093/infdis/jiy027

Cited by 15 publications

(14 citation statements)

References 23 publications

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“…This pattern was observed in other countries in the region, with a record number of infections notified in Australia, and an unusually prolonged season in Hong Kong. 27,28 Similar findings have also been reported from the Northern hemisphere 2017/18 winter. 29 These seasons have been dominated by A/H3N2 and estimates of vaccine effectiveness against this subtype have been low.…”

Section: Discussionsupporting

confidence: 75%

Semiannual Versus Annual Influenza Vaccination in Older Adults in the Tropics: An Observer-blind, Active-comparator–controlled, Randomized Superiority Trial

Young

Sadarangani

Haur

et al. 2018

Clinical Infectious Diseases

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Background: Antibody titres and vaccine effectiveness decline within six months after influenza vaccination in older adults. Biannual vaccination may be necessary to provide year-round protection in the tropics where influenza is present throughout the year. Methods: Tropical Influenza Control Strategies (TROPICS1) was a single-centre, 1:1 randomised, observer-blinded, active-comparator controlled, superiority study in 200 community-resident adults aged ≥65 years. Participants received standard-dose trivalent inactivated influenza vaccination (IIV3) at enrolment, and either tetanus-diphtheria-pertussis vaccination or IIV3 six months later. Primary outcome was the proportion of participants with haemagglutination-inhibition (HI) geometric mean titre (GMT) ≥1:40 one month after the second vaccination (Month 7). Secondary outcomes included GMTs to Month 12, the incidence of influenza-like illness (ILI), and adverse reactions after vaccination. This study is registered with ClinicalTrials.gov: NCT02655874. Findings: At Month 7, the proportion of participants with a HI tire ≥1:40 against A/H1N1 increased by 21•4% (95% CI 8•6-33•4) in the six-monthly vaccination group. This proportion was not significantly higher for A/H3N2 (4•3, 95% CI-1•1-10•8) or B (2•1, 95% CI-2•0-7•3). Six-monthly vaccination significantly increased GMTs against A/H1N1 and A/H3N2 at Month 7, but not B. Participants receiving repeat IIV3 reported a significantly lower incidence of ILI in the six months after the second vaccination (relative vaccine efficacy of 57•1%, 95% CI 0•6-81•5). The frequency of adverse events was similar after first or second influenza vaccination. Interpretation: Six-monthly influenza vaccination in older residents of tropical countries is a simple intervention with the potential for improving protection against infection.

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Section: Discussionsupporting

confidence: 75%

Semiannual Versus Annual Influenza Vaccination in Older Adults in the Tropics: An Observer-blind, Active-comparator–controlled, Randomized Superiority Trial

Young

Sadarangani

Haur

et al. 2018

Clinical Infectious Diseases

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“…We analysed data from a test-negative study designed to monitor influenza VE against hospitalization in children in Hong Kong across 5 years from 1 September 2012 through 31 August 2017. 16–19 Children between 6 months and 17 years of age were included in the analysis if they were admitted to general wards in four public hospitals in Hong Kong with fever ≥38°C and any respiratory symptom such as runny nose, cough or sore throat. As previously described, 16–19 nasopharyngeal aspirates were collected from all eligible children and initially tested by direct immunofluorescence assay and then subsequently tested by culture and reverse transcription polymerase chain reaction (RT-PCR).…”

Section: Methodsmentioning

confidence: 99%

“…In this established study, we previously reported influenza VE against hospitalization in children in 2009–2013, 16 in 2009–2014 for influenza B viruses, 17 in 2015/16, 18 and in 2016/17. 19 Here, we analysed data from five consecutive years to assess how influenza VE changes by time intervals between vaccination and hospitalization, taking advantage of almost year-round circulation of influenza in Hong Kong.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of influenza vaccination on influenza-associated hospitalisations over time among children in Hong Kong: a test-negative case-control study

Feng

Chiu

Chan

et al. 2018

The Lancet Respiratory Medicine

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Background: The protection conferred by influenza vaccination is generally thought to last less than a year, necessitating annual re-vaccination. However, the speed with which influenza vaccine effectiveness (VE) might decline during a year is unknown. This is of particular importance for locations with year-round influenza activity. Methods: We analysed data from a test-negative study of influenza VE in hospitalized children in Hong Kong over five consecutive years. We examined how VE changed by time between vaccination and hospitalisation. Findings: We analysed data on 15,695 children admitted from September 2012 through August 2017. Among study participants, the majority of vaccinations occurred in the final quarter of each year. Influenza admissions occurred year-round with peaks in January through March in most years and a large summer peak in 2016. We estimated that VE against influenza A or B decreased from 79% (95% CI: 64%−88%) for children vaccinated within 0.5 to 2 months, to 60% (95% CI: 46%−71%) within 2 to 4 months, to 57% (95% CI: 39%−70%) within 4–6 months of vaccination, and to 45% (95% CI: 22%−61%) within 6–9 months of vaccination. In separate analyses by type/subtype, we estimated that VE declined by 2–5 percentage points per month. Interpretation: We observed clear evidence of reductions in VE during the 9 months after vaccination in children. Our findings confirm the importance of annual vaccination in children. Influenza vaccines that provide broader and longer-lasting protection are needed to provide year-round protection in regions with irregular influenza seasonality or prolonged periods of influenza activity.

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“…We enrolled children who were admitted with a febrile acute respiratory illness (ARI) to the general paediatric wards in these three hospitals. Febrile ARI was defined as fever measured ≥ 38 °C plus any respiratory symptom such as cough, sore throat or runny nose [3-5]. Healthcare staff collected nasopharyngeal aspirates from all enrolled children and tested for influenza viruses by reverse transcriptase PCR.…”

Section: Study Participantsmentioning

confidence: 99%

“…Previous influenza A(H1N1)pdm09 epidemics occurred in 2012/13, 2013/14 and 2015/16 [3,4]. Here we continued an ongoing study [3-5] using the test-negative design [6,7] to estimate influenza vaccine effectiveness (VE) in hospitalised children in Hong Kong in the early part of the 2018/19 winter influenza season.…”

mentioning

confidence: 99%

Early season estimate of influenza vaccination effectiveness against influenza hospitalisation in children, Hong Kong, winter influenza season 2018/19

Chiu

Kwan²,

Feng

et al. 2019

Eurosurveillance

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The winter 2018/19 influenza season in Hong Kong has been predominated by influenza A(H1N1)pdm09 as at January 2019. We enrolled 2,016 children in three public hospitals in Hong Kong between 2 September 2018 and 11 January 2019. Using the test-negative approach, we estimated high early season effectiveness of inactivated influenza vaccine against influenza A or B of 90% (95% confidence interval (CI): 80–95%) and 92% (95% CI: 82–96%) against influenza A(H1N1)pdm09.

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Influenza Vaccine Effectiveness Against Influenza A(H3N2) Hospitalizations in Children in Hong Kong in a Prolonged Season, 2016/2017

Abstract: Influenza vaccination was effective in preventing hospitalizations in children in Hong Kong.

Cited by 15 publications

References 23 publications

Semiannual Versus Annual Influenza Vaccination in Older Adults in the Tropics: An Observer-blind, Active-comparator–controlled, Randomized Superiority Trial

Semiannual Versus Annual Influenza Vaccination in Older Adults in the Tropics: An Observer-blind, Active-comparator–controlled, Randomized Superiority Trial

Effectiveness of influenza vaccination on influenza-associated hospitalisations over time among children in Hong Kong: a test-negative case-control study

Early season estimate of influenza vaccination effectiveness against influenza hospitalisation in children, Hong Kong, winter influenza season 2018/19

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