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Vaccination rates for pandemic influenza among pregnant women: An early observation from Chennai, South India

Context: World Health organization considers pregnancy as an important risk factor for severe illness due to pandemic influenza and recommends better vaccination coverage for them. Aims: This study was initiated to observe the vaccination rates among pregnant women in Chennai during 2 months following the availability of influenza vaccine in the region. Settings and Design: An urban community-based setting. Questionnaire-based observational study design. Materials and Methods: Pregnant women residing in Chennai selected by simple random sampling formed the study population. The study was conducted from 15th to 30th November 2010. Each pregnant woman was interviewed using a uniform questionnaire. Statistical Analysis Used: Characteristics between vaccinated and unvaccinated participants were compared using the Chi-square test or the Fisher exact test for categorical variables and Student's t-test or Mann-Whitney U test for continuous variables. Results: 140 pregnant women were interviewed during the study period. The mean age of study participants was 25 years (range 21-35 years). 55% were less than 26 years of age and 65% were home makers. 32% had no basic school education. Of the 29 women with co-morbidities, 15 had gestational diabetes, 13 hypertension, 7 pre-eclampsia, and 7 had bronchial asthma. Fifty-eight had anemia diagnosed earlier or during current pregnancy. 32 (22.8%) were given advice to get vaccinated for pandemic influenza of which 18 (12.8%) received the vaccine. Conclusions: Observations on vaccination rates for pandemic influenza among pregnant women in Chennai, 2 months after the initiation of vaccination program is not encouraging.


INTRODUCTION
World Health Organization (WHO) considers pregnancy as one among the three physiological risk factors (others being age less than 2 year or more than 65 years) for severe disease due to novel 2009 H1N1 influenza virus and strongly recommends vaccination for them irrespective of the period of gestation. [1,2] Changes in immune status, cardiac, and respiratory systems are likely reasons for an increased severity of influenza in pregnancy. [3] A large the post-pandemic period," the report also mentions that the virus will circulate among community as a seasonal influenza virus in the years to come and individuals with high-risk for severe infection will continue to be susceptible and need adequate vaccination to prevent severe illness. [6] The Tamil Nadu state government introduced the vaccination program on September 14 th 2010 at King Institute, Guindy, Chennai. [7] The vaccine was available at private vaccination centers in Chennai about 2 weeks earlier itself. This community-based study was initiated to identify the vaccination rates for pandemic influenza among pregnant women in Chennai during the first 2 months after the launch of influenza vaccine and to analyze factors associated with vaccination or otherwise.

MATERIALS AND METHODS
Pregnant women residing in Chennai on follow-up with either government or private outpatient clinics who were selected by simple random sampling formed the study population. The study was conducted from 15 to 30 November 2010. Residences of pregnant women were located by volunteers of Community Research Network (CRN) with the help of local social health workers, retired health inspectors, and obstetricians followed by house visit by one of the study authors. Regions of Chennai were broadly divided into North, Central, and South Chennai. Each region was further divided into three sub-divisions each separated from other by at least 6 km. Patients residing in each sub-division were questioned on the same day. Order of patient enrolment in the study was based on proximity of patient's residence to the place where the investigators began the process of questioning on a given day. Each pregnant woman was interviewed about details of her age, educational status, permanent residence, current gestational period, number of pregnancies, vaccination status for pandemic influenza, advice received on need for vaccination in pregnancy, reason for not getting vaccinated despite medical advice, whether a patient asked about the need for influenza vaccination to medical professional, details of doctors consulted during pregnancy, total number of medical visits, pre-existing medical co-morbidities, and current pregnancy-related medical complications. After completion of questionnaire if the participant is found unvaccinated, a brief session of counseling was given about the benefits of influenza vaccination, address of government and private agencies delivering the vaccine, details of cost, and guidance on reaching the vaccination sites using public transport. Informed oral consent was obtained from study participants. The CRN ethics committee approved the study.

Statistical analysis
Continuous variables were expressed as mean (range) and categorical variables were expressed as number (%). Differences in baseline characteristics between vaccinated and unvaccinated participants and factors associated with vaccine acceptance among participants who were advised vaccination were studied using the Chi-square test or Fisher's exact test for categorical variables and Student's t-test or Mann-Whitney U test for continuous variables. A P value <0.05 was considered to be statistically significant. Analysis was carried out with SPSS version 12.

RESULTS
A total of 140 pregnant women were visited and interviewed during the study period. None of the visited participant refused to be interviewed. Participants were residing in Chennai for at least 6 months before the onset of study. Baseline characteristics of study participants are shown in Table 1. The mean age of study participants was 25 years (range 21-35 years). Most of them were less than 26 years of age and were home makers. 80 (57%) were permanent residents of Chennai, while the remaining were primarily based outside Chennai (45 (32%) from urban regions and 15 (11%) from rural regions of south India) and have come to Chennai due to cultural or social reasons. Nearly one-third did not receive any basic school education. Forty-eight were pregnant for the first time, while 92 had at least one living child. Most were in their third trimester. Of the 29 women with co-morbidities, 15 had gestational diabetes, 13 hypertension, 7 pre-eclampsia, and 7 had bronchial asthma. Fifty-eight had anemia

DISCUSSION
The pandemic influenza vaccination rate of 12.8% observed in our study is clearly sub-optimal to prevent serious influenza illness among pregnant women. Vaccination rates against seasonal influenza among pregnant women in the United States were consistently low before the present 2009 pandemic (24% during 2007-2008 season and 11.3% during 2008-2009 season). [8] However, estimates of vaccination coverage among pregnant women in 10 regions in United States during the current pandemic had been historically high with a rate of 46.6%. [8] In the present study, only 22.8% of study participants were advised by a health care provider to receive the vaccine. In comparison, 75.2% pregnant women were advised to receive the flu shot in the United States. [8] Since in India, routine seasonal influenza vaccination is not administered to pregnant women in the past, advice on receiving the H1N1 vaccine, place of vaccine availability, advantages of vaccine to mother and fetus, safety of vaccine, and cost is highly desirable if provided by health-care providers.
Our study observation that most individuals who were advised vaccine by their obstetrician received the vaccine highlights the impact of advice by the primary clinician.
Although the present study observed that advice by other specialty doctors and health workers was not as successful as an obstetrician's advice it should not discourage them from giving advice on benefits of flu vaccination. Studies in the United States have shown that advice by health-care provider on vaccination and availability of vaccine at their clinic had resulted in better vaccination rates. [8] Despite government efforts to spread the message on the need for vaccination through health workers, poster display, and media advertisement, it appears that they are less effective. Although the study could not identify the reason for this, it appeared that television is the most frequent communication media accessed by most pregnant women and private channels are more frequently viewed than government channels probably due to more entertainment content in the former. It may be prudent to suggest that government can encourage private partnership in media coverage of influenza vaccination programs in the near future. The study also suggests the importance of educating the spouse on benefits of vaccination to mother and fetus. The fact that only 4 of 32 women in the present study who were advised vaccination had fear about the safety of vaccine is encouraging since the proportion of patients who refuse vaccination due to reasons related to safety of vaccine is higher in western countries. [8,9] The study does have important limitations. First, the sample does not represent the entire group of pregnant women in Chennai during the study period. This limitation could not be averted since registries on pregnant women in public and private sector health clinics were not available. Although it can be argued that the representation should be based on birth rates in different regions of the city which could lessen the risk of a poor representative sample, a substantial number of births happening in Chennai were of women who have just migrated to the city for safe confinement and may not reflect the regional representation of pregnant women residing in Chennai. The second limitation is of possible geographical bias and the results of the present study should not be interpolated to sub-urban regions outside the main divisions of Chennai (north, south, and central) and probably other parts of the state.
To conclude, observation on vaccination rates for pandemic influenza among pregnant women in Chennai, 2 months after the initiation of vaccination program is not encouraging. A better involvement from health care providers especially obstetricians with support from other specialists may improve vaccination rates. Educating the spouse of pregnant women about benefits of vaccine and involvement of private audio-visual media in the spreading the message can yield favorable results.