Vaccination during the 2013-2014 influenza season in pregnant Japanese women

Safety of influenza vaccination during pregnancy: a systematic review

OBJECTIVE

We conducted a systematic review to evaluate associations between influenza vaccination during pregnancy and adverse birth outcomes and maternal non-obstetric serious adverse events (SAEs), taking into consideration confounding and temporal biases.

METHODS

Electronic databases (Ovid MEDLINE ALL, Embase Classic+Embase and the Cochrane Central Register of Controlled Trials) were searched to June 2021 for observational studies assessing associations between influenza vaccination during pregnancy and maternal non-obstetric SAEs and adverse birth outcomes, including preterm birth, spontaneous abortion, stillbirth, small-for-gestational-age birth and congenital anomalies. Studies of live attenuated vaccines, single-arm cohort studies and abstract-only publications were excluded. Records were screened using a liberal accelerated approach initially, followed by a dual independent approach for full-text screening, data extraction and risk of bias assessment. Pairwise meta-analyses were conducted, where two or more studies met methodological criteria for inclusion. The Grading of Recommendations, Assessment, Development and Evaluation approach was used to assess evidence certainty.

RESULTS

Of 9443 records screened, 63 studies were included. Twenty-nine studies (24 cohort and 5 case-control) evaluated seasonal influenza vaccination (trivalent and/or quadrivalent) versus no vaccination and were the focus of our prioritised syntheses; 34 studies of pandemic vaccines (2009 A/H1N1 and others), combinations of pandemic and seasonal vaccines, and seasonal versus seasonal vaccines were also reviewed. Control for confounding and temporal biases was inconsistent across studies, limiting pooling of data. Meta-analyses for preterm birth, spontaneous abortion and small-for-gestational-age birth demonstrated no significant associations with seasonal influenza vaccination. Immortal time bias was observed in a sensitivity analysis of meta-analysing risk-based preterm birth data. In descriptive summaries for stillbirth, congenital anomalies and maternal non-obstetric SAEs, no significant association with increased risk was found in any studies. All evidence was of very low certainty.

CONCLUSIONS

Evidence of very low certainty suggests that seasonal influenza vaccination during pregnancy is not associated with adverse birth outcomes or maternal non-obstetric SAEs. Appropriate control of confounding and temporal biases in future studies would improve the evidence base.

Maternal vaccination-current status, challenges, and opportunities

AIM

Maternal vaccination is a promising strategy for protecting pregnant women and newborns against severe infections. This review aims to describe the current status and challenges associated with maternal vaccination against seasonal influenza, tetanus-diphtheria-pertussis (Tdap/DTaP), and novel coronavirus disease of 2019 (COVID-19) in Japan and other countries, mainly the United States and the United Kingdom.

METHODS

A literature search was conducted in PubMed and other public websites (e.g., Centers for Disease Control and Prevention) to obtain information on maternal vaccination.

RESULTS

Inactivated vaccines are recommended for pregnant women by gynecologic societies in Japan, the United States, and the United Kingdom. Among pregnant Japanese women, the influenza and COVID-19 (two doses) vaccine coverage rates were 27.0%-53.5% (six studies) and 73.6% (one study), respectively; there are no studies on maternal vaccination with DTaP. Concerns regarding vaccine safety are a major barrier to maternal vaccination across countries. Maternal vaccination is effective in preventing severe disease in pregnant women and protecting infants aged <6 months, is generally safe, and does not increase the risk of adverse maternal and fetal outcomes. Providing accurate information regarding vaccination through healthcare providers and the government and government funding for vaccines may help improve maternal vaccination rates in Japan.

CONCLUSION

Current coverage for maternal vaccination is still low globally mainly because of vaccine hesitancy among pregnant women. The government, drug-regulatory authorities, and healthcare professionals must educate pregnant women about the effectiveness and safety of maternal vaccines and encourage vaccination when the benefits outweigh the risks.

Disease burden of respiratory syncytial virus infection in the pediatric population in Japan

INTRODUCTION

Respiratory syncytial virus (RSV) is one of the most common causes of lower respiratory tract infections in children aged <5 years and is associated with long-term respiratory morbidities such as recurrent wheezing and asthma, decreased lung function, and allergic sensitization. The objective of this review was to evaluate the epidemiology and burden of RSV infection in the pediatric population in Japan.

METHODS

Studies indexed in PubMed and ICHUSHI databases during January 2010-December 2020 were manually reviewed. Data on proportion of RSV infections, seasonality, length of stay (LoS), mortality, medical expenses, and palivizumab use were extracted from the selected articles.

RESULTS

Ninety-three articles were included (PubMed, 64; ICHUSHI, 29). The proportion of patients/samples with an RSV infection was 5.5%-66.7%, and 6.0%-29.9% in the inpatient and outpatient departments, respectively. RSV infections generally occurred during autumn/winter; however, recently the peak has shifted to summer. The LoS was variable and depended on factors such as age, infection severity, wheezing, and RSV subgroups. Mortality rates varied from <1% to 19% depending on the infection severity. The average daily hospitalization and intensive care unit cost was JPY 34,548 while intensive care unit incurred an additional cost of JPY 541,293. Palivizumab was indicated for high-risk infants and 0%-3% of patients required hospitalization despite palivizumab use.

CONCLUSIONS

RSV imposes a significant burden on the Japanese healthcare system, suggesting a need to create awareness among caregivers of children, pregnant women and healthcare professionals to ensure early recognition of infection and adequate treatment or prophylaxis.

Epidemiology and burden of illness of seasonal influenza among the elderly in Japan: A systematic literature review and vaccine effectiveness meta-analysis

BACKGROUND

Elderly populations are particularly vulnerable to influenza and often require extensive clinical support. In Japan, nationwide passive surveillance monitors seasonal influenza but does not capture the full disease burden. We synthesized existing evidence on the epidemiology, vaccine effectiveness (VE), and economic burden of seasonal influenza in the elderly population.

METHODS

PubMed, EMBASE, and ICHUSHI were searched for articles on seasonal influenza in Japan, published between 1997 and 2018, in English or Japanese. Grey literature was also assessed. A random-effects meta-analysis characterized VE of influenza vaccines among studies reporting this information.

RESULTS

Of 1,147 identified articles, 143 met inclusion criteria. Reported incidence rates varied considerably depending on study design, season, study setting and, most importantly, case definition. In nursing homes, the maximum reported attack rate was 55.2% and in the 16 articles reporting mortality rates, case fatality rates varied from 0.009% to 14.3%. Most hospitalizations were in people aged >60; healthcare costs were partially mitigated by vaccine administration. Meta-analysis estimated overall VE of 19.1% (95% CI: 2.3% - 33.0%) with a high proportion of heterogeneity (I2 : 89.1%). There was a trend of lower VE in older people (40.1% [-57.3-77.2] in the <65 group; 12.9% [-8.0-29.8] in those 65; P = .21).

CONCLUSIONS

Despite differences between studies that make comparisons challenging, the influenza burden in elderly Japanese is significant. While vaccines are effective, current vaccination programs offer suboptimal protection. Health economic data and cost-effectiveness analyses were limited and represent areas for policy-relevant future research.

Cost-effectiveness analysis of influenza vaccination during pregnancy in Japan

BACKGROUND

Pregnant women and infants are known as high risk groups for influenza. WHO recommend pregnant women be vaccinated with inactivated influenza vaccine. In Japan, some municipalities started to give subsidy to encourage pregnant women to receive a shot on their own accord, which has made the introduction of seasonal antepartum maternal vaccination program (AMVP) into the routine vaccination list a current topic in health policy and has raised the need to evaluate the value for money of such possibility.

METHODS

We conducted a cost-effectiveness analysis to evaluate the efficiency of conducting AMVP in Japan. A decision tree model was adopted taking into consideration the duration of single-year vaccine effectiveness for infants and for mothers. The program targeted pregnant women aged 20-49 years old at or over 12 weeks gestation during October 1 through March 30. Estimated probabilities of treatments received due to influenza for pregnant/postpartum women or their infants varied by calendar time, vaccination status, and/or gestational age. Incremental cost-effectiveness ratio (ICER) compared with current no-AMVP from societal perspective was calculated. Transition probabilities, utility weights to estimate quality-adjusted life year (QALY), and disease treatment costs were either calculated or extracted from literature. Costs per vaccination was assumed at ¥3,529/US$32.1.

RESULTS

AMVP reduces disease treatment costs, while the reduction cannot offset the vaccination cost. Incremental QALYs were at 0.00009, among them 84.2% were from infants. ICER was ¥7,779,356/US$70,721 per QALY gained. One-way sensitivity analyses revealed that vaccine effectiveness for infant and costs per shot were the two main key variables affecting the ICER.

CONCLUSION

We found that vaccinating pregnant women with influenza vaccine to prevent unvaccinated infants and pregnant/postpartum women from influenza-associated disease in Japan can be cost-effective from societal perspective, under the WHO-suggested "cost-effective" criteria (1-3 times of GDP).

Maternal influenza vaccination relates to receiving relevant information among pregnant women in Japan

Maternal vaccination for seasonal influenza is currently not listed as a routine vaccination in the national vaccination schedule of Japan. However, many pregnant women voluntarily receive an influenza vaccination. We explored the factors related to influenza vaccine uptake. We particularly focused on factors related to any recommendation, such as advice or suggestions from another individual. We conducted a cross-sectional web-based questionnaire survey in Japan among pregnant women or mothers who had recently given birth in March 2017 and 2018. Logistic regression models were used to determine the factors influencing vaccination uptake. Key individuals regarding maternal vaccination were examined using the network visualization software Gephi. The total number of valid responses was 2204 in 2017 and 3580 in 2018. Over 40% of respondents had been vaccinated with the seasonal influenza vaccine at some point in both years. Of the vaccinated respondents, over 80% received advice regarding the influenza vaccination. Obstetricians were the most common source of advice in both years. Among respondents who chose more than two sources, the largest link in the network of sources was found between the obstetrician and family members. Attention to public concern or potential recommenders, by public health authorities, not just pregnant women, about the benefits of maternal influenza vaccination is important.

Are social inequalities in influenza vaccination coverage in Japan reduced by health policy?

Influenza vaccination is effective to prevent influenza infection. However, findings about association between socioeconomic status and influenza vaccination coverage are controversial. Online survey was conducted among 4995 participants between 20 and 69 years of age throughout Japan, January 2017. We asked about history of receiving vaccination in previous year and socioeconomic status, with their reasons for having vaccination or not. Age stratified multivariable logistic regression model was conducted to estimate the odds ratio (ORs) and 95% confidence intervals (CIs) of receiving vaccine for each educational level and income. Sex, self-reported health status, marital status and income were included as covariates. The rate for receiving influenza vaccine among ≤64 year-olds and ≥65 year-olds was 32.9% and 35.4%, respectively. Among younger adults, vaccination varied by each education: junior high school, 23.6%; senior high school, 27.2%; college, 32.6%; university, 36.2%; and graduate school, 39.8%. Compared to junior high school, those from graduate school tended to be more vaccinated (OR1.88, 95%CI 1.07–3.24). On the contrary, those aged above ≥65 years old received vaccination with no significant differences across education. Likewise, among respondents aged ≤64 year-olds, income was significantly associated with influenza vaccination. Despite being “Managed by school or company” (32.5%), having “No particular reason” was the frequent reason for both receiving influenza vaccination (23.8%) or not (34.3%). Adults with higher educational level were significantly more likely to receive vaccination. Subsidizing influenza vaccination may reduce inequality in receiving vaccination for adults. Strengthening vaccination through various approaches is necessary, such as managing by school or company.

The effects of OLL1073R-1 yogurt intake on influenza incidence and immunological markers among women healthcare workers: a randomized controlled trial

This randomized controlled trial did not show the effects of OLL1073R-1 yogurt intake on influenza prevention and NK cell activity enhancement. However, a significant increase in IFN-γ production was demonstrated.

Analysis of public concerns about influenza vaccinations by mining a massive online question dataset in Japan

BACKGROUND

Elucidating public concerns regarding vaccinations is important for successful immunization programs. The objective of the present study was to categorize public concerns regarding influenza vaccinations in Japan by analyzing a massive web-based question dataset.

METHODS

The Yahoo! Chiebukuro (Japanese Yahoo! Answers) Dataset, which includes more than 16 million questions collected between April 2004 and April 2009, was used in this study. We sequentially filtered data to obtain questions on influenza vaccinations. Any questions that met our exclusion criteria concerning veterinary vaccines or computer virus vaccines were removed from the analysis. Filtered questions and their answers were manually analyzed for their content by a team of board-certified pediatricians.

RESULTS

After filtering data, we obtained 1950 questions regarding influenza vaccinations. The three most frequently asked questions were regarding the vaccination schedule, safety, and effectiveness. When we analyzed monthly trends in question contents, we noted the emergence of similar questions in the same period every year. Therefore, we classified the time periods of each year into three parts: (1) from April to the commencement of seasonal influenza vaccinations (September), (2) from October until the epidemic period, and (3) the epidemic period. Two interesting results were obtained: concerns regarding effectiveness abruptly increased during the epidemic period, and pregnant or breastfeeding women increasingly asked questions regarding feasibility between October and the epidemic period.

CONCLUSIONS

The questions and concerns collected and analyzed in this study illustrate that the public have questions about the influenza vaccine and also that questions changed with periodical consistency. These results highlight the possible usefulness of providing the public with the latest and correct information to their questions in a timely manner, for example via an official health website.