2009 H1N1 vaccination by pregnant women during the 2009-10 H1N1 influenza pandemic


Pregnant women were identified at greater risk and given priority for 2009 H1N1 vaccination during the 2009 through 2010 H1N1 pandemic. We identified factors associated with acceptance or refusal of 2009 H1N1 vaccination during pregnancy.

Study Design

We conducted an in-person survey of postpartum women on the labor and delivery service from June 17 through Aug. 13, 2010, at 4 New York hospitals.


Of 1325 survey respondents, 34.2% received 2009 H1N1 vaccination during pregnancy. A provider recommendation was most strongly associated with vaccine acceptance (odds ratio [OR], 19.4; 95% confidence interval [CI], 12.7–31.1). Also more likely to take vaccine were women indicating the vaccine was safe for the fetus (OR, 12.4; 95% CI, 8.3–19.0) and those who previously took seasonal flu vaccination (OR, 7.9; 95% CI, 5.8–10.7). Race, education, income, and age were less important in accepting vaccine.


Greater emphasis on vaccine safety and provider recommendation is needed to increase the number of women vaccinated during pregnancy.

In 2009, the H1N1 virus, a combination of human, swine, and avian influenza, emerged and led to a worldwide pandemic. The 2009 H1N1 virus spreads similar to other influenza viruses by respiratory droplets and through mucosal contact with respiratory secretions from infected persons. Early reports identified pregnant women at much higher risk for hospitalization and intensive care unit admission as well as mortality. The Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices and the Institute of Medicine strongly recommended pregnant women be vaccinated against the 2009 H1N1 virus.

Although efforts have been made to raise awareness about the importance of vaccinating pregnant women against influenza, there is a long-standing reluctance among pregnant women to be vaccinated. Even with increased morbidity during pregnancy from seasonal influenza only 11% of pregnant women were vaccinated during the 2008 through 2009 flu season. During the 2009 H1N1 pandemic, vaccination coverage among pregnant women ranged from 21.4-46.6%. While influenza vaccination is considered safe during pregnancy to the mother and fetus, perceived safety issues with the vaccine have been cited as the primary reason for lack of acceptance. In addition, influenza vaccination is often not offered by obstetrical practices.

During the 2009 H1N1 influenza pandemic, the importance of vaccination was widely publicized and pregnant women were given high priority for receipt of vaccine. However, it was observed that relatively few pregnant women took advantage of the regional department of health free vaccination program and we were uncertain whether pregnant women were receiving vaccine from other sources. In this survey we determined the frequency of 2009 H1N1 vaccination in postpartum women. The main objectives were to determine reasons for lack of acceptance, including those related to knowledge and safety perception. Because there is a wide range of incomes and educational background in our region we also determined the role of sociodemographic factors in accepting vaccine.

Materials and Methods

This was a survey of postpartum women on the labor and delivery service at 4 hospitals: 3 in Nassau County, New York, and 1 located in Queens County, New York. Nassau County has a population of 1,357,429 and a median household income of $94,856. Queens County, located in New York City and adjacent to the western border of Nassau County, has a population of 2,306,712 with a median household income of $55,599. Three of the surveyed hospitals were voluntary institutions and 1 was a county municipal hospital.

The surveys were done from June 17, 2010, through Aug. 13, 2010. We attempted to consecutively sample all women on the inpatient obstetric service by having trained surveyors approach postpartum women ≥24 hours after a live delivery. The goals of the survey were explained to potential participants and each was asked whether she received the 2009 H1N1 vaccine during her pregnancy. Women who answered the vaccine acceptance question were then asked to respond to a survey that took about 10 minutes to complete. The surveys were administered daily at each of the hospitals and attempts were made to reach all women who delivered prior to hospital discharge. When there were language barriers, a translation telephone service was used to administer the survey.

The survey instrument contained questions regarding receipt of the 2009 H1N1 vaccine, attitudes toward receipt of vaccination during pregnancy, perceived safety of vaccination, perception of the 2009 H1N1 viral syndrome, reasons for not taking 2009 H1N1 vaccine, and the role of the outpatient obstetric medical provider in vaccination. Age, census tract (as determined by the home address), insurance status, and race/ethnicity were recorded. Race and ethnicity were determined by the participants completing the survey and were obtained to determine if vaccination acceptance differed by background. For the questions addressing perception or opinion, there were 4 potential responses: strongly agree, somewhat agree, somewhat disagree, and strongly disagree.

For purposes of data analysis, responses to the categorical questions were collapsed from strongly agree/somewhat agree to agree and from somewhat disagree/strongly disagree to disagree. Descriptive statistics and χ 2 testing were performed as indicated. Unadjusted and adjusted odds ratios (ORs) were calculated using logistic regression. Age, race, income, and education were included a priori as adjustment variables. In building models, the c-statistic and Nagelkerke pseudo R 2 were used to assess the strength of association between selected variables and receipt of vaccination. All statistical calculations were conducted using R statistical software and SAS/STAT software, version 9.2 (SAS Institute, Cary, NC). Census tracts were identified using the home address and the World Wide Web tool, geocoding system (Tele Atlas; Federal Financial Institutions Examination Council website). The median family income of the census tract was used as an estimate of family income.

The project was developed as an after-action program based on observations that very few pregnant women received vaccine from local health department–coordinated sites, and the survey was designed to better understand the low vaccination acceptance. The database did not contain any identifiers, and the Human Subjects Review Committee of North Shore-LIJ Health System/Feinstein Institute for Medical Research determined that the program did not require review.


There were 2210 deliveries at the 4 hospitals during the study period and a total of 1429 women were approached prior to their hospital discharge. There were 1090/1429 (76%) women who responded to the full survey, 226/1429 (16%) who answered only the 2009 H1N1 acceptance question, 27/1429 (2%) who refused to answer any 2009 H1N1-related questions, 77/1429 (5%) who were not available for the survey or unable to answer any questions due to medical-related issues, and 9/1429 (0.6%) who responded to the full survey but were unsure whether they received vaccine or not.

Among the regions where the respondents lived, there were 47.3% of women who resided in Nassau County, 39.7% in Queens County, 8.4% in neighboring Suffolk County, and 4.5% in other areas. Background information on women who completed the full survey is shown in Table 1 . The median age was 31 years (range, 14–47 years), 49% were white, 88% had some form of third-party payer insurance, and 62% of women had completed college or graduate school. There were 67% of women who had an estimated annual income of <$75,000.


Respondent characteristics

Maternal age group, y n (%)
≥35 300 (27.3)
25-34 660 (60.1)
<25 139 (12.6)
White, non-Hispanic 538 (49.0)
Black, non-Hispanic 135 (12.3)
Asian, non-Hispanic 127 (11.6)
Other, non-Hispanic 57 (5.2)
Hispanic 242 (22.0)
Graduate degree 321 (29.2)
College graduate 355 (32.3)
High school 322 (29.3)
<High school 76 (6.9)
Missing/unknown 25 (2.3)
County of residence
Nassau 503 (45.8)
Queens 447 (40.7)
Suffolk 98 (8.9)
Other 51 (4.6)
Hospital of service
Voluntary A 416 (37.9)
Voluntary B 425 (38.7)
Voluntary C 140 (12.7)
Municipal D 118 (10.7)
Health insurance
Private 965 (87.8)
Self-pay 23 (2.1)
Medicaid 105 (9.6)
Missing/unknown 6 (0.5)
Median census tract income ($)
≥75,000 358 (32.6)
50,000-75,000 501 (45.6)
<50,000 186 (16.9)
Missing/unknown 54 (4.9)

Dlugacz. 2009 H1N1 vaccination during pregnancy. Am J Obstet Gynecol 2012.

2009 H1N1 influenza-related knowledge and vaccine safety perceptions are reported in Table 2 . A total of 42% of women indicated that 2009 H1N1 vaccine should be avoided during pregnancy and 35% indicated the vaccine could hurt the unborn baby. Most women recognized the potential seriousness of 2009 H1N1 influenza during pregnancy with 94% indicating the virus could cause hospitalization or death. Almost all women indicated they trusted their medical provider to give them good advice regarding the 2009 H1N1 vaccination.


Survey questions of vaccine safety perception, provider involvement, and 2009 H1N1 influenza knowledge

Survey question Agree Disagree Missing
Do you believe all vaccinations should be avoided during pregnancy? 382 (34.8) 705 (64.1) 12 (1.1)
Do you believe that 2009 H1N1 vaccine should be avoided during pregnancy? 457 (41.6) 618 (56.2) 24 (2.2)
Do you believe that 2009 H1N1 vaccine increases chances/risks of miscarriage or birth defects? 313 (28.5) 72 (65.6) 65 (5.9)
Do you believe that receiving 2009 H1N1 vaccine during pregnancy hurts the unborn baby? 381 (34.7) 664 (60.4 54 (4.9)
Do you believe that nonpregnant women should be worried about receiving 2009 H1N1 vaccination? 407 (37.0) 670 (61.0) 22 (2.0)
Are you concerned that 2009 H1N1 vaccine could cause you to develop fever or other flu-like symptoms? 627 (57.1) 456 (41.5) 16 (1.5)

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May 23, 2017 | Posted by in GYNECOLOGY | Comments Off on 2009 H1N1 vaccination by pregnant women during the 2009-10 H1N1 influenza pandemic
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