Adverse events following influenza A (H1N1) 2009 monovalent vaccines reported to the Vaccine Adverse Event Reporting System,United States,October 1, 2009–January 31, 2010

The United States (US) influenza A (H1N1) 2009 monovalent (2009-H1N1) vaccination program began in October 2009. Reports to the vaccine adverse event reporting system (VAERS), a US spontaneous reporting system, were reviewed to identify potential rare events or unusual adverse event (AE) patterns after 2009-H1N1 vaccination. The adverse event profile after 2009-H1N1 vaccine in VAERS (∼10,000 reports) was consistent with that of seasonal influenza vaccines, although the reporting rate was higher after 2009-H1N1 than seasonal influenza vaccines, this may be, at least in part, a reflection of stimulated reporting. Death, Guillain–Barré syndrome and anaphylaxis reports after 2009-H1N1 vaccination were rare (each <2 per million doses administered).     

Pandemic and seasonal vaccine coverage and effectiveness during the 2009–2010 pandemic influenza in an Italian adult population

Objectives

To evaluate the response to pandemic vaccination and seasonal and pandemic vaccine effectiveness (VE) in an Italian adult population, during the 2009?C2010 influenza season.

Methods

Data were recorded by interviewing 19,275 subjects (??35?years), randomly recruited from the general population of the Moli-sani project. Events [influenza-like illness (ILI), hospitalization and death], which had occurred between 1 November 2009 and 31 January 2010 were considered. VE was analyzed by multivariable Poisson regression analysis.

Results

Pandemic vaccine coverage was very low (2.4%) in subjects at high-flu risk, aged 35?C65?years (N?=?8,048); there was no significant preventive effect of vaccine against ILI. Seasonal vaccine coverage was 26.6% in the whole population (63% in elderly and 21.9% in middle-aged subjects at high-flu risk). There was a higher risk to develop ILI in middle-age [VE: ?17% (95% CI: ?35,?1)] or at high flu-risk [VE: ?17% (95% CI: ?39, 2)] vaccinated groups.

Conclusions

Coverage of pandemic vaccine was very low in a Southern Italy population, with no protective effect against ILI.     

Phase II trial in adults of concurrent or sequential 2009 pandemic H1N1 and 2009–2010 seasonal trivalent influenza vaccinations

BackgroundDuring the 2009 influenza pandemic both seasonal and 2009 pandemic vaccines were recommended. We conducted a randomized trial of monovalent 2009-H1N1 vaccine and seasonal trivalent inactivated influenza vaccine (IIV3) given sequentially or concurrently to adults.MethodsAdults randomized to 4 study groups and stratified by age (18–64 and ≥65 years) received 1 dose of seasonal IIV3 or placebo and 2 doses of 2009-H1N1 vaccine or placebo in one of 4 combinations, i.e., H1N1 + Placebo/H1N1 + Placebo/IIV3 (HP/HP/V3), H1N1 + IIV3/H1N1 + Placebo/Placebo (HV3/HP/P), H1N1 + Placebo/H1N1 + IIV3/Placebo (HP/HV3/P), and IIV3 + Placebo/H1N1 + Placebo/H1N1 (V3P/HP/H). Intramuscular injections were given three times at 21 day intervals. Sera for antibody assays were obtained prior to and 21 days after each vaccination. Reactogenicity and adverse events were monitored.ResultsEight hundred-five (805) adults were enrolled. All combinations of vaccines were safe and well tolerated. In general, one dose of 2009-H1N1 and one dose of IIV3, regardless of sequence or concurrency of administration, were immunogenic in adults. There were no significant differences in geometric mean titers (GMT) or the proportions of subjects with ≥4-fold rise in antibody responses and titers ≥40 for any vaccine group or between age strata for 2009-H1N1 after the first or second dose, although the vaccine sequence affected the titers to the IIV3 antigens. Hemagglutination inhibition antibody (HAI) GMTs against 2009-H1N1 for the combined age strata 21 days after the first 2009-H1N1 dose were 190.4, 182.1, 232.9 and 157.5 for HP/HP/V3, HV3/HP/P, HP/HV3/P and V3P/HP/H, respectively. While IIV3 GMTs were adequate they were generally lower than the 2009-H1N1 GMTs. In a subset of subjects, there was good correlation between HAI and microneutralization (MN) titers (Spearman's correlation coefficient 0.92).ConclusionsAll vaccine combinations were generally well tolerated. Immune responses to one dose of 2009-H1N1 were adequate regardless of the sequence of vaccination in all age groups, but the sequence affected titers to IIV3 antigens.     

Trends in U.S. hospitalizations and inpatient deaths from pneumonia and influenza, 1996–2011

BackgroundTo reduce excess morbidity and mortality of pneumonia and influenza (PI), the Advisory Committee on Immunization Practices has recommended the use of 7-valent pneumococcal conjugate vaccine (PCV7), and incrementally expanded the target group for annual influenza vaccination of healthy persons, to ultimately include all persons ≥6 months of age without contraindications as of the 2010–2011 influenza season. We aimed to capture broader epidemiologic changes by looking at PI collectively.MethodsUsing interrupted time series, we evaluated the changes in the rates of PI hospitalization and inpatient death across three periods defined according to the changes in vaccination policy. We assessed linear trends adjusting for seasonality, sex, and age group, allowing for differential impact across age groups. PI hospitalizations were defined as a principal diagnosis of PI, or a principal diagnosis of sepsis or respiratory failure, accompanied by a secondary diagnosis of PI.ResultsOverall annual rates of PI hospitalizations and inpatient deaths declined by 95 per 100,000 (95% CI: 45–145) and by 4.4 per 100,000 (95% CI: 0.9–7.8), respectively. This translates to 295,000 fewer PI hospitalizations and 13,600 fewer PI inpatient deaths than expected based on the average rates from 1996 through 1999. PI hospitalizations dropped the most among seniors aged 65+ by 487 per 100,000, followed by children aged <2, by 228 per 100,000. PI inpatient deaths declined most among seniors aged 65+, by 25.3 per 100,000.ConclusionsIn this nationally representative study, PI hospitalizations and inpatient deaths decreased in U.S. between 1996 and 2011. There is a temporal association with the introduction and widespread use of pneumococcal conjugate vaccines, and the expansion of the target group for annual influenza vaccination to include all persons ≥6 months of age, while it is difficult to attribute these changes directly to specific vaccines used in this era.     

Seasonal influenza vaccine supply and target vaccinated population in China, 2004–2009

To better understand the gap between limited influenza vaccine supply and the target population for vaccination in China, we conducted a retrospective survey to quantify the production capacity, supply and sale of seasonal trivalent inactive vaccine (TIV) from the 2004–2005 through the 2008–2009 season, and estimated the target population who should receive annual influenza vaccine. The maximum domestic capacity to produce TIV was 126 million doses in 2009. A total of 32.5 million doses of TIV were supplied in 2008–2009, with an average annual increase rate of 18% from 16.9 million in 2004–2005. This represents an amount sufficient to vaccinate 1.9% of Chinese population. The average number of doses of TIV for sale by province ranged from <5 to 108 per 1000 people. The differences are explained in part by level of economic development but also influenced by local reimbursement policies in some provinces. Based on national recommendations, we estimated a target population of 570.6 million or 43% of the total population. Supply and domestic production capacity for influenza vaccine is currently insufficient to vaccinate the estimated target population in China. The Government of China should consider measures to improve domestic production capacity of influenza vaccine, expand successful promotional campaigns, and add cost subsidies in high risk groups to further encourage influenza vaccine usage.     

Impact of influenza vaccination on mortality in the French elderly population during the 2000–2009 period

With declining influenza vaccine coverage in the elderly in recent years in France, we aimed at assessing the benefits of seasonal influenza vaccination, based on available data for observed mortality, vaccine coverage and vaccine effectiveness.To estimate the annual number of deaths avoided by vaccination in the people aged 65 years or more, we used the following three elements: an estimate of vaccine effectiveness against all-cause mortality (based on the “difference-in-differences” approach which reduces the usual bias seen in observational studies), French mortality data and vaccine coverage data.We estimated an annual average of 2000 deaths currently avoided through vaccination and a vaccine effectiveness of 35% against influenza-attributable deaths. Around 2650 vaccinations are needed to prevent a death among the elderly.Communicating these results should help restoring at-risk populations’ confidence in influenza vaccination.     

Sustained high influenza vaccination rates and decreased safety concerns among pregnant women during the 2010–2011 influenza season

Objective

Intense efforts to vaccinate pregnant women against 2009 H1N1 influenza resulted in much higher vaccine uptake than previously reported. We surveyed postpartum women to determine whether high vaccination rates were sustained during the 2010–11 influenza season.

Methods

We performed cross-sectional surveys of postpartum women delivering at our institution during February–April 2010 and February–March 2011. The surveys ascertained maternal characteristics, history of influenza vaccination, and reasons for lack of vaccination.

Results

During the 2010–11 season, 165 (55%) of 300 women surveyed reported receiving influenza vaccination, compared to 191 of 307 (62%) during 2009–10 (p = 0.08). Vaccination by an obstetrical provider was common, but decreased compared to 2009–10 (60% vs. 71%, p = 0.04). While most women (76%) in 2010–11 reported that their provider recommended influenza vaccination, significantly more reported lack of discussion about vaccination (24% vs. 11%, p < 0.01) compared to 2009–10. Vaccine safety concerns were cited by most (66%) women declining vaccination during 2009–10 but only 27% of women who declined in 2010–11.

Conclusion

The vaccination rate among pregnant women at our institution was relatively sustained, although fewer providers appear to be discussing influenza vaccination in pregnancy. Concern about vaccine safety, the primary barrier during 2009–10, was much less prominent.     

Immunogenicity and safety of AS03-adjuvanted 2009 influenza A H1N1 vaccine in children 6–35 months

We report on the evaluation of the immunogenicity and reactogenicity/safety of AS03-adjuvanted vaccine against pandemic influenza A/H1N1/2009 in young children. In this open-label, randomized study, 157 healthy children aged 6–35 months received two doses (21 days apart) of split-virion inactivated A/California/7/2009 H1N1 vaccine containing either (i) 1.9 μg hemagglutinin (HA) and AS03_B (5.93 mg tocopherol) (N = 104) or (ii) 3.75 μg HA and AS03_A (11.86 mg tocopherol) (N = 53). At 21 days following the first dose of AS03_B-adjuvanted vaccine (1.9 μg HA) the percentage of children with hemagglutination-inhibition titers of ≥40 against the vaccine strain rose from 3.0% before vaccination to 100%. The seroconversion rate was 99% and the geometric mean titer (GMT) increased from 6 to 313. After the second dose the GMT increased further to 2008. The higher dose AS03_A-adjuvanted 3.75 μg HA vaccine did not further increase the immune response. Solicited symptoms reported within 7 days following vaccination were mainly mild to moderate. After the first dose of AS03_B-adjuvanted vaccine (1.9 μg HA) the most common solicited symptoms were pain at the injection site (35.6%) and irritability (31.7%). Fever (axillary ≥37.5 °C) was reported with an incidence of 20.2%. After the second dose reactogenicity tended to increase (injection site pain: 41.3%; irritability: 46.2%; fever ≥37.5 °C: 67.3%). Spontaneously reported adverse events with an intensity that prevented normal activities were documented for 2.9–6.7% of doses with only one event (vomiting) considered related to vaccination. There was one serious adverse event reported in the AS03_A-adjuvanted 3.75 μg HA vaccine group (traumatic brain injury) which was not considered as related to vaccination. In conclusion, these data suggest that a first dose of AS03_B-adjuvanted A/H1N1/2009 vaccine containing 1.9 μg HA in children 6–35 months old is highly immunogenic and that the overall reactogenicity profile is acceptable although reactions including fever tend to increase after a second dose.     

Surveillance of perceptions,knowledge, attitudes and behaviors of the Italian adult population (18–69 years) during the 2009–2010 A/H1N1 influenza pandemic

Monitoring perceptions, knowledge, attitudes and behaviors of populations during pandemic flu outbreaks is important as it allows communication strategies to be adjusted to meet emerging needs and assessment to be made of the effects of recommendations for prevention. The ongoing Italian Behavioral Risk Factor Surveillance System (PASSI) offered the setting for investigating people’s opinions and behaviors regarding the A/H1N1 pandemic. PASSI surveillance is carried out in 126/148 Italian Local Health Units (LHU) through monthly telephone interviews administered by public health staff to a random sample of the resident population 18–69 years. In fall 2009 additional questions exploring issues related to the A/H1N1 flu were added to the standard questionnaire. The pandemic module was administered on a voluntary basis by the 70 participating LHUs from November 2nd, 2009 to February 7th, 2010; 4 047 interviews were collected. Overall 33% of respondents considered it likely that they would catch flu, 26% stated they were worried, 16% reported having limited some daily activities out of home and 22% said they would accept vaccination if offered. All these indicators showed a decreasing trend across the four-month period of observation. The most trusted sources of information were family doctors (81%). Willingness to be vaccinated was associated with worry about pandemic, age, sex, having a chronic disease and timing of the interview. The surveillance allowed us to gather relevant information, crucial for devising appropriate public health interventions. In future disease outbreaks, systems monitoring people’s perceptions and behaviors should be included in the preparedness and response plans.     

HIV Screening Practices and Hospital Characteristics in the U.S., 2009–2010

Objectives

The Centers for Disease Control and Prevention recommends HIV screening in U.S. health-care settings unless providers document a yield of undiagnosed HIV infections of <1 per 1,000 population. However, implementation of this guidance has not been widespread and little is known of the characteristics of hospitals with screening practices in place. We assessed how screening practices vary with hospital characteristics.

Methods

We used a national hospital survey of HIV testing practices, linked to HIV prevalence for the county, parish, borough, or city where the hospital was located, to assess HIV screening of some or all patients by hospitals. We used multivariate logistic regression analysis to assess the association between screening practices and hospital characteristics that were significantly associated with screening in bivariate analyses.

Results

Of 376 hospitals in areas of prevalence ≥0.1%, only 25 (6.6%) reported screening all patients for HIV and 131 (34.8%) reported screening some or all patients. Among 638 hospitals included, screening some or all patients was significantly (p<0.05) more common at teaching hospitals, hospitals with higher numbers of annual admissions, and hospitals with a high proportion of Medicaid admissions. In multivariable analysis, screening some or all patients was independently associated with admitting more than 15% of Medicaid patients and receiving resources or reimbursement for screening tests.

Conclusion

We found that few hospitals surveyed reported screening some or all patients, and failure to screen is common across all types of hospitals in all regions of the country. Expanded reimbursement for screening may increase compliance with the recommendations.Of the 1.2 million people in the United States who are infected with human immunodeficiency virus (HIV), it is estimated that 20% are unaware of their infection.¹ Early diagnosis of HIV infection allows infected people to obtain treatment that can prolong the quality and duration of their lives and can lead to reductions in high-risk behaviors and HIV transmission.^2–8 More generally, HIV infection satisfies the usual criteria for routine screening for infectious disease: it is a serious health disorder that can be diagnosed before symptoms appear; it can be detected by a reliable, noninvasive test; there are great potential health benefits to early detection; and the benefits of detection are large relative to the cost of screening.⁹ For these reasons, and to reduce the number of undiagnosed people living with HIV, in 2006 the Centers for Disease Control and Prevention (CDC) recommended HIV screening in all health-care settings for all individuals aged 13–64 years, regardless of risk, seen at facilities with an HIV prevalence of undiagnosed infections ≥0.1% among a sample of patients, and annual screening for patients known to be at risk for HIV infection.¹⁰Previous research has shown that the teaching status and size of hospitals, as well as the region and type of metropolitan area in which they are located, are associated with the availability of HIV testing in hospitals.¹¹ However, there are few published data about hospital characteristics that are associated with the adoption of CDC''s revised testing recommendations, and existing studies do not consider the impact of external factors, such as state regulations or third-party reimbursement policies, that might influence whether hospitals adopt the testing guidelines. Also unknown is how the screening practices of hospitals that serve larger proportions of low-income and minority patients compare with the practices of other hospitals.To address these open questions, we assessed the association between characteristics of hospitals and adoption of CDC''s revised recommendations for HIV testing in health-care settings using data from a national hospital survey of HIV testing practices in 2009. The results of that national survey, comparing responses in 2009 with those from 2004, have been previously reported.¹² However, that report did not consider factors that might influence screening practices, such as county HIV prevalence, information on state HIV testing regulations, and information on the percentage of admissions of low-income and minority patients at participating hospitals.     

Intradermal and virosomal influenza vaccines for preventing influenza hospitalization in the elderly during the 2011–2012 influenza season: A comparative effectiveness study using the Valencia health care information system

Background

The use of intradermal vaccination or virosomal vaccines could increase protection against influenza among the vulnerable population of older adults. Studies assessing the comparative effectiveness of these two influenza vaccine types in this age group are lacking.

Methods

We conducted a retrospective cohort study to estimate the comparative effectiveness of intradermal seasonal trivalent-influenza vaccine (TIV) delivered by a microneedle injection system and a virosomal-TIV intramuscularly delivered for prevention of influenza hospitalization in non-institutionalized adults aged ≥65 years. We obtained administrative data on immunization status and influenza hospitalization for the 2011–2012 influenza season, and used Cox regression models to assess comparative effectiveness. We estimated crude and adjusted (age, sex, comorbidity, pharmaceutical claims, recent pneumococcal vaccination and number of hospitalizations for all causes other than influenza between the previous and current influenza seasons) hazard ratios (HR).

Results

Overall, 164,021 vaccinated subjects were evaluated. There were 127 hospitalizations for influenza among 62,058 subjects, contributing 914,740 person-weeks at risk in the virosomal-TIV group, and 133 hospitalizations for influenza among 101,963 subjects, contributing 1,504,570 person-weeks at risk in the intradermal-TIV group. The crude HR of intradermal-TIV relative to virosomal-TIV was 0.64 (95% confidence interval (CI): 0.50–0.81), and the adjusted Cox estimated HR was 0.67 (95% CI: 0.52–0.85).

Conclusions

During the 2011–2012 influenza season the risk of hospitalization for influenza was reduced by 33% in non-institutionalized elderly adults who were vaccinated with intradermal-TIV compared with virosomal-TIV.     

Reports of cell-based influenza vaccine administered during pregnancy in the Vaccine Adverse Event Reporting System (VAERS), 2013–2020

BackgroundIn November 2012, the first cell cultured influenza vaccine, a trivalent subunit inactivated influenza vaccine (Flucelvax(®), ccIIV3), was approved in the United States for adults aged ≥18 years. A quadrivalent version (ccIIV4) was later approved in 2016 and replaced ccIIV3. The safety of ccIIV3 or ccIIV4 (ccIIV) was not assessed for pregnant women or their infants during pre-licensure studies.ObjectiveTo assess the safety of ccIIV administered during pregnancy in pregnant women and their infants whose reports were submitted to VAERS during 2013–2020.Material and methodsWe searched VAERS for United States reports of adverse events (AEs) in pregnant women who received ccIIV from 1 July 2013 through 31 May 2020. Clinicians reviewed reports and available medical records and assigned a primary clinical category for each report. Reports were coded as serious based on the Code of Federal Regulations definition.ResultsVAERS received 391 reports following ccIIV administered to pregnant women. Twenty-four (6.1%) were serious. Two neonatal deaths were reported. No maternal deaths occurred. Among reports with trimester information (n = 340), ccIIV was administered during the second trimester in 170 (50%). The most frequent pregnancy-specific AE was premature delivery in 85 (21.7%) reports, followed by dysmature placenta in 13 (3.3%) and pre-eclampsia/eclampsia in ten (2.3%). The most common non-pregnancy specific conditions were infectious conditions in 32 (8.2%). Among infant conditions, low birth weight was reported in 62 (15.9%) reports. Fifteen birth defects were reported; in 12 with gestational age information, administration of the vaccine occurred late in the second trimester or later.ConclusionsReview of maternal ccIIV reports in VAERS was not unexpectedly different from other maternal influenza vaccine safety VAERS reviews.     

Effectiveness of the current and prior influenza vaccinations in Northern Spain, 2018–2019

BackgroundThe population targeted for influenza vaccination can be repeatedly vaccinated over successive seasons, and vaccines received in previous seasons may retain preventive effect. This study aims to estimate the effectiveness of inactivated influenza vaccines received in the current and prior seasons in the 2018–2019 season.MethodsInfluenza-like illness patients attended by sentinel general practitioners or admitted to hospitals in Navarre, Spain, were tested for influenza. Vaccination status in the current and three prior seasons was obtained from the vaccination registry. The test-negative design was used to estimate the vaccine effectiveness.ResultsA total of 381 influenza A(H1N1)pdm09 cases, 341 A(H3N2) cases and 1222 controls were analysed. As compared to individuals unvaccinated in the current and three prior seasons, the influenza vaccine effectiveness against A(H1N1)pdm09 was 57% (95% confidence interval [CI]: 40%, 70%) for current season vaccination regardless of prior doses and 48% (95%CI: 14%, 68%) for vaccination in prior seasons but not in the current season. These estimates were 12% (95%CI: −23%, 37%) and 27% (95%CI: −22%, 56%), respectively, against influenza A(H3N2). Individuals vaccinated with the two A(H1N1)pdm09 strains in influenza vaccines since 2009, A/Michigan/45/2015 and A/California/07/2009, had higher protection (68%; 95%CI: 53%, 77%) than those vaccinated with A/Michigan/45/2015 only (29%, p = 0.020) or with A/California/07/2009 only (34%, p = 0.005).ConclusionThese results suggest moderate effectiveness of influenza vaccination against A(H1N1)pdm09 and low effectiveness against A(H3N2) influenza in the 2018–2019 season. Vaccination in prior seasons maintained a notable protective effect. Strains included in previous vaccines were as effective as the current vaccine strain, and both added their effects against influenza A(H1N1)pdm09.     

Survey of distribution of seasonal influenza vaccine doses in 201 countries (2004–2015): The 2003 World Health Assembly resolution on seasonal influenza vaccination coverage and the 2009 influenza pandemic have had very little impact on improving influenza control and pandemic preparedness

There is no global monitoring system for influenza vaccination coverage, making it difficult to assess progress towards the 2003 World Health Assembly (WHA) vaccination coverage target. In 2008, the IFPMA Influenza Vaccine Supply International Task Force (IVS) developed a survey method to assess the global distribution of influenza vaccine doses as a proxy for vaccination coverage rates. The latest dose distribution data for 2014 and 2015 was used to update previous analyses. Data were confidentially collected and aggregated by the IFPMA Secretariat, and combined with previous IFPMA IVS survey data (2004–2013). Data were available from 201 countries over the 2004–2015 period. A “hurdle” rate was defined as the number of doses required to reach 15.9% of the population in 2008. Overall, the number of distributed doses progressively increased between 2004 and 2011, driven by a 150% increase in AMRO, then plateaued. One percent fewer doses were distributed in 2015 than in 2011. Twenty–three countries were above the hurdle rate in 2015, compared to 15 in 2004, but distribution was highly uneven in and across all WHO regions. Three WHO regions (AMRO, EURO and WPRO) accounted for about 95% of doses distributed. But in EURO and WPRO, distribution rates in 2015 were only marginally higher than in 2004, and in EURO there was an overall downward trend in dose distribution. The vast majority of countries cannot meet the 2003 WHA coverage targets and are inadequately prepared for a global influenza pandemic. With only 5% of influenza vaccine doses being distributed to 50% of the world’s population, there is urgency to redress the gross inequities in disease prevention and in pandemic preparedness. The 2003 WHA resolution must be reviewed and revised and a call issued for the renewed commitment of Member States to influenza vaccination coverage targets.     

Obstetricians and the 2009–2010 H1N1 Vaccination Effort: Implications for Future Pandemics

Our objective was to describe the experiences of obstetricians during the 2009–2010 H1N1 vaccination campaign in order to identify possible improvements for future pandemic situations. We conducted a cross-sectional mail survey of a national random sample of 4,000 obstetricians, fielded in Summer 2010. Survey items included availability, recommendation, and patient acceptance of H1N1 vaccine; prioritization of H1N1 vaccine when supply was limited; problems with H1N1 vaccination; and likelihood of providing vaccine during a future influenza pandemic. Response rate was 66 %. Obstetricians strongly recommended H1N1 vaccine during the second (85 %) and third (86 %) trimesters, and less often during the first trimester (71 %) or the immediate postpartum period (76 %); patient preferences followed a similar pattern. H1N1 vaccine was typically available in outpatient obstetrics clinics (80 %). Overall vaccine supply was a major problem for 30 % of obstetricians, but few rated lack of thimerosal-free vaccine as a major problem (12 %). Over half of obstetricians had no major problems with the H1N1 vaccine campaign. Based on this experience, 74 % would be “very likely” and 12 % “likely” to provide vaccine in the event of a future influenza pandemic. Most obstetricians strongly recommended H1N1 vaccine, had few logistical problems beyond limited vaccine supply, and are willing to vaccinate in a future pandemic. Addressing concerns about first-trimester vaccination, developing guidance for prioritization of vaccine in the event of severe supply constraints, and continued facilitation of the logistical aspects of vaccination should be emphasized in future influenza pandemics.     

Birth outcomes following immunization of pregnant women with pandemic H1N1 influenza vaccine 2009–2010

BackgroundFollowing the H1N1 influenza pandemic in 2009, pregnant women were recommended to receive both seasonal (TIV) and H1N1 influenza vaccines. This study presents incidence of adverse birth and pregnancy outcomes among a population of pregnant women immunized with TIV and H1N1 vaccines at Kaiser Permanente Northern California during 2009–2010.MethodsWe telephone surveyed pregnant Kaiser Permanente Northern California members to assess non-medically-attended reactions following H1N1, TIV or both vaccines during 2009–2010 (n = 5365) in a separate study. Here we assessed preterm birth (<37 weeks), very preterm birth (<32 weeks), low birth weight (<2500 g, LBW), very low birth weight (<1500 g), small for gestational age, spontaneous abortions, stillbirths and congenital anomalies among this cohort by comparing incidence and 95% confidence intervals between the following immunization groups: TIV only, H1N1 only, H1N1 prior to TIV immunization, TIV prior to H1N1 and both immunizations given at the same time.ResultsResults did not vary significantly between groups. Comparing H1N1 with TIV, incidence were similar for preterm births (6.37 vs 6.28/100 births), very preterm births (5.30 vs 8.29/1000 births), LBW (4.19 vs 2.90/100 births), very LBW (4.54 vs 5.52/1000 births), small for gestational age (9.99 vs 9.24/1000 births), spontaneous abortion (7.10 vs 6.83/1000 pregnancies), stillbirths (7.10 vs 4.57/1000 pregnancies), and congenital anomalies (2.66 vs 2.43/100 births).ConclusionsAlthough constrained by small sample size, complex vaccine groups, and differential vaccine availability during 2009–2010, this study found no difference in adverse birth outcomes between H1N1 vaccine and TIV.