Effectiveness of Partial and Full Influenza Vaccination Among Children Aged &lt;9 Years in Hong Kong, 2011–2019

Chua, Huiying; Chiu, Susan S.; Chan, Eunice C.; Feng, Luzhao; Kwan, Mike Yat Wah; Wong, Joshua S C; Peiris, Malik; Cowling, Benjamin J.

doi:10.1093/infdis/jiz361

Cited by 8 publications

(5 citation statements)

References 42 publications

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“…This finding is consistent with antibody immune response and limited observational studies o f b o t h o u t p at i e nt s a n d i n p at i e nt s i n t h e US a n d elsewhere. [20][21][22][23][24][25] Among partially vaccinated children overall, we detected statistically significant VE, which has been reported in fewer studies. 10,26,27 However, 1 dose of vaccine in the current season did not provide statistically significant protection against laboratory-confirmed influenza among the small proportion of previously unvaccinated children aged 2 years or younger.…”

Section: Discussionmentioning

confidence: 92%

“…Our study suggests a benefit of receiving 2 doses of inactivated influenza in the first season of vaccination as well as full vaccination as recommended by the ACIP. This finding is consistent with antibody immune response and limited observational studies of both outpatients and inpatients in the US and elsewhere . Among partially vaccinated children overall, we detected statistically significant VE, which has been reported in fewer studies .…”

Section: Discussionmentioning

confidence: 99%

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Patterns of Influenza Vaccination and Vaccine Effectiveness Among Young US Children Who Receive Outpatient Care for Acute Respiratory Tract Illness

et al. 2020

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IMPORTANCEThe burden of influenza among young children is high, and influenza vaccination is the primary strategy to prevent the virus and its complications. Less is known about differences in clinical protection following 1 vs 2 doses of initial influenza vaccination.OBJECTIVES To describe patterns of influenza vaccination among young children who receive outpatient care for acute respiratory tract illness in the US and compare vaccine effectiveness (VE) against medically attended laboratory-confirmed influenza by number of influenza vaccine doses received.DESIGN This test-negative case-control study was conducted in outpatient clinics, including emergency departments, at 5 sites of the US Influenza Vaccine Effectiveness Network during the 2014-2015 through 2017-2018 influenza seasons. The present study was performed from November 5, 2014, to April 12, 2018, during periods of local influenza circulation. Children aged 6 months to 8 years with an acute respiratory tract illness with cough who presented for outpatient care within 7 days of illness onset were included. All children were tested using real-time, reverse-transcriptase polymerase chain reaction for influenza for research purposes.EXPOSURES Vaccination in the enrollment season with either 1 or 2 doses of inactivated influenza vaccine as documented from electronic medical records, including state immunization information systems. MAIN OUTCOMES AND MEASURESMedically attended acute respiratory tract infection with real-time, reverse-transcriptase polymerase chain reaction testing for influenza. RESULTSOf 7533 children, 3480 children (46%) were girls, 4687 children (62%) were non-Hispanic white, and 4871 children (65%) were younger than 5 years. A total of 3912 children (52%) were unvaccinated in the enrollment season, 2924 children (39%) were fully vaccinated, and 697 children (9%) were partially vaccinated. Adjusted VE against any influenza was 51% (95% CI, 44%-57%) among fully vaccinated children and 41% (95% CI, 25%-54%) among partially vaccinated children. Among 1519 vaccine-naive children aged 6 months to 2 years, the VE of 2 doses in the enrollment season was 53% (95% CI, 28%-70%), and the VE of 1 dose was 23% (95% CI, −11% to 47%); those who received 2 doses were less likely to test positive for influenza compared with children who received only 1 dose (adjusted odds ratio, 0.57; 95% CI, 0.35-0.93).CONCLUSIONS AND RELEVANCE Consistent with US influenza vaccine policy, receipt of the recommended number of doses resulted in higher VE than partial vaccination in 4 influenza seasons. Efforts to improve 2-dose coverage for previously unvaccinated children may reduce the burden of influenza in this population.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Patterns of Influenza Vaccination and Vaccine Effectiveness Among Young US Children Who Receive Outpatient Care for Acute Respiratory Tract Illness

et al. 2020

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“…We also found that the SPRs of a one-dose regimen in participants who had received two or more doses were comparable to those of a two-dose regimen in vaccineunprimed participants. A study in Hong Kong reported that the vaccine effectiveness induced by a one-or two-dose vaccination regimen was 73% and 31%, respectively, in children aged 6 months through 9 years receiving influenza vaccination for the first time [11]. Another effectiveness study in Japan revealed that both one-and two-dose regimens of IIV significantly reduced cases of any influenza among children aged 1-12 years; however, only the two-dose regimen was significantly effective in preventing influenza B in certain influenza seasons [12].…”

Section: Discussionmentioning

confidence: 99%

Immunogenicity and Safety of One versus Two Doses of Quadrivalent Inactivated Influenza Vaccine (IIV4) in Vaccine-Unprimed Children and One Dose of IIV4 in Vaccine-Primed Children Aged 3–8 Years

Shi,

Yang,

et al. 2023

Vaccines

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Two doses of the inactivated influenza vaccine (IIV) are generally recommended for children under 9 years old. This study assessed the necessity for a second dose of quadrivalent IIV (IIV4) in children aged 3–8 years. In this randomized, open-label, paralleled-controlled study, 400 children aged 3–8 years who were vaccine-unprimed were randomly assigned at a 1:1 ratio to receive a two-dose (Group 1) or one-dose (Group 2) regimen of IIV4, and 200 who were vaccine-primed received one dose of IIV4 (Group 3). A serum sample was collected before and 28 days after the last dose to determine the hemagglutination inhibition (HI) antibody level. Adverse events were collected within 28 days after each dose. One-dose or two-doses of IIV4 were well tolerated and safe in children aged 3–8 years, and no serious adverse events related to the vaccine were reported. The seroconversion rates (SCRs) of HI antibody ranged from 61.86% to 95.86%, and the post-vaccination seroprotection rates (SPRs) were all >70% in three groups against the four virus strains. The two-dose regimen in vaccine-unprimed participants (Group 1) achieved similar SPRs in comparison with the one-dose in the vaccine-primed group (Group 3), and the SPRs in Group 1 and Group 3 were higher in vaccine-unprimed participants of the one-dose regimen (Group 2). The present study supports the recommendations of a two-dose regimen for IIV4 use in children aged 3–8 years.

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“…These two studies suggested that annual influenza vaccination is 40%-60% effective against LCI hospitalization in young children; however, the estimates included LAIVs and were not restricted to IIVs. More recent studies (146)(147)(148)(149)(150)(151) have rather found high VE rates against LCI hospitalization (up to 81%) in young children (Table 2).…”

Section: Vaccine Efficacy/effectiveness and Other Benefits Of Iivs In Children Under 5 Yearsmentioning

confidence: 92%

Safety, Immunogenicity, Efficacy and Effectiveness of Inactivated Influenza Vaccines in Healthy Pregnant Women and Children Under 5 Years: An Evidence-Based Clinical Review

2021

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Annual influenza vaccination is often recommended for pregnant women and young children to reduce the risk of severe influenza. However, most studies investigating the safety, immunogenicity, and efficacy or effectiveness of influenza vaccines are conducted in healthy adults. In this evidence-based clinical review, we provide an update on the safety profile, immunogenicity, and efficacy/effectiveness of inactivated influenza vaccines (IIVs) in healthy pregnant women and children <5 years old. Six electronic databases were searched until May 27, 2021. We identified 3,731 articles, of which 93 met the eligibility criteria and were included. The IIVs were generally well tolerated in pregnant women and young children, with low frequencies of adverse events following IIV administration; however, continuous vaccine safety monitoring systems are necessary to detect rare adverse events. IIVs generated good antibody responses, and the seroprotection rates after IIVs were moderate to high in pregnant women (range = 65%–96%) and young children (range = 50%–100%), varying between the different influenza types/subtypes and seasons. Studies show vaccine efficacy/effectiveness values of 50%–70% in pregnant women and 20%–90% in young children against lab-confirmed influenza, although the efficacy/effectiveness depended on the study design, host factors, vaccine type, manufacturing practices, and the antigenic match/mismatch between the influenza vaccine strains and the circulating strains. Current evidence suggests that the benefits of IIVs far outweigh the potential risks and that IIVs should be recommended for pregnant women and young children.

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Effectiveness of Partial and Full Influenza Vaccination Among Children Aged <9 Years in Hong Kong, 2011–2019

Cited by 8 publications

References 42 publications

Patterns of Influenza Vaccination and Vaccine Effectiveness Among Young US Children Who Receive Outpatient Care for Acute Respiratory Tract Illness

Patterns of Influenza Vaccination and Vaccine Effectiveness Among Young US Children Who Receive Outpatient Care for Acute Respiratory Tract Illness

Immunogenicity and Safety of One versus Two Doses of Quadrivalent Inactivated Influenza Vaccine (IIV4) in Vaccine-Unprimed Children and One Dose of IIV4 in Vaccine-Primed Children Aged 3–8 Years

Safety, Immunogenicity, Efficacy and Effectiveness of Inactivated Influenza Vaccines in Healthy Pregnant Women and Children Under 5 Years: An Evidence-Based Clinical Review

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