currently the influenza vaccine is recommended in the united states for all individuals over 6 months of age   and by the world health organization for high - risk groups .
these recommendations have , in part , the aim to reduce the worldwide estimated deaths 250,000500,000 each year caused by the seasonal form of the disease .
pregnant women are included in these recommendations because vaccination with the inactivated virus has been shown to decrease the burden of suffering among neonates [ 46 ] and to reduce maternal morbidity of the infection .
furthermore , vaccination in pregnancy has been documented as sufficiently safe to be recommended to be given regardless of trimester [ 4 , 8 ] .   despite these recommendations in pregnancy ,
coverage of pregnant women in the united states has been low in the years prior to the 2009 - 2010 influenza season ( 11% to 24% ) .
reasons cited for this include not being offered the vaccine , not having the vaccine in the office , and maternal concerns for vaccine safety [ 9 , 10 ] . in the spring of 2009 , a new swine - origin form of the influenza a virus , causing substantial morbidity and mortality , was isolated : h1n1 . as part of the pandemic strategy for this virus ,
a specific monovalent vaccine for h1n1 was developed and was ready for distribution in the fall of 2009 . among the high - risk groups targeted to receive this vaccine , in addition to the seasonal vaccine , were pregnant women .
the rationale for this included the high mortality rates associated with influenza among pregnant women in earlier pandemics   and early reports of the severity of h1n1 illness in pregnancy , [ 1416 ] which proved to be true as the 2009 to 2010 influenza season progressed [ 17 , 18 ] .
recently , population - based data on vaccine coverage of pregnant women in the united states during the 2009 - 2010 pandemic were published by the centers for disease control ( cdc ) .
this report revealed less than full coverage during that season despite a robust public - health response , with self - reported coverage rates of 51% for the seasonal vaccine and 47% for the h1n1 vaccine .
the purpose of this study is to compare these national rates to those in a public safety - net hospital system serving a large number of uninsured patients , using chart - verified documentation of vaccination .
this was a retrospective cohort study of pregnant patients who delivered at maricopa medical center during the 2009 - 2010 influenza pandemic . in order to be eligible ,
subjects must have received prenatal care at the hospital or one of the nine associated prenatal clinics preceding their delivery .
it serves as a public safety - net facility for maricopa county ( population 3.8 million ) which includes phoenix , arizona .
efforts to promote influenza vaccine coverage for pregnant patients during the 2009 - 2010 influenza season included education of providers via grand rounds , small group in - service sessions , and emailed recommendations for clinicians providing prenatal and intrapartum care .
standing orders for nursing staff to administer the vaccine without a physician signature were also written and distributed .
indirect efforts to promote vaccination included activities to increase awareness , such as signage regarding influenza , distribution and implementation of influenza - like illness ( ili ) protocols , phone followup of ili patients not requiring admission , and backup call schedules for attending physicians , as well as infection control activities with screening of patients and visitors for ili in our health care facilities .
we did not have an electronic medical record with a vaccine registry to identify prospectively those who had not been previously vaccinated . in order to be consistent with the cdc 's study  
we included births which occurred from when the vaccines were first available in our health system , september 15 , 2009 for the seasonal vaccine and october 15 , 2009 for the h1n1 vaccine .
a random sample of subjects was selected for review from a billing database of 939 deliveries which occurred during the september 15 , 2009 to april 30 , 2010 time frame .
charts were first reviewed for eligibility : receipt of prenatal care at mihs . at the beginning of the chart review ,
a sample of charts ( the first 10 charts by each reviewer ) was reviewed by a second reviewer to assure accurate capture of the study variables .
in addition , in order to be certain that vaccine administration was not missed in the chart review , a second review of charts with no documented vaccination was undertaken by a different reviewer .
predictor variables were also collected during the chart review and included age at delivery , gestational age at delivery , race / ethnicity , patient language , and gravidity and parity .
the outcome was receipt of the seasonal vaccine and/or the h1n1 vaccine as determined by documentation on progress notes or vaccination forms .
our targeted sample size was 200 , which would allow us to be at least 95% certain that the observed vaccination rate falls within 6.9% of the true value .
prevalence rates of vaccine coverage and 95% confidence intervals were calculated for the 2 vaccines for different time periods as noted in section 3 .
chi - square statistics were used to determine statistical significance with a p value of < 0.05 considered significant .
this study was approved by the mihs institutional review board via expedited review on november 10 , 2011 .
  a random sample of 296 of the 939 deliveries which occurred in the study time frame was reviewed . of these
the seasonal influenza sample comprised a total of 246 women who delivered between september 15 , 2009 and april 30 , 2010 , and the h1n1 sample comprised .
217 who delivered between october 15 , 2009 and april 30 , 2010 table 1 provides a description of the seasonal influenza sample .
the sample was representative of our population ; mainly hispanic , non - english speaking , without insurance , and of high parity .   in the seasonal influenza sample
, 132 of the 246 subjects ( 54% ) received the seasonal vaccine , ( 95% confidence interval , 48% to 60% ) . in order to more directly compare the rates with national rates as presented by the cdc ,
the sample was restricted to births occurring until march 12 , 2010 . of these 216 subjects
, 61% received the vaccine ( 95% confidence interval , 55% to 68% ) .   in the h1n1 sample
, 111 of 217 ( 51% ) received the h1n1 vaccine , ( 95% confidence interval , 44% to 58% ) . in the sample restricted to births through march 12 , 2010 , 111 of 187 ( 59% ) received the h1n1 vaccine ( 95% confidence interval , 52% to 66% ) .   the corresponding rate for receipt of both vaccines from october 15 , 2009 to april 30 , 2010 was 33% ( 72 of 217 ) ( 95% confidence interval , 27% to 40% ) . when restricted to births through march 12 , 2010 ,
the corresponding rate was 39% ( 72 of 187 ; 95% confidence interval , 32% to 46% ) .  
our commitment to vaccinate against influenza required extra , nonroutine efforts in the form of education and mandatory separate written orders or 
standing orders ,  both of which involved separate paperwork . to understand the role of the additional documentation effort , we compared rates of influenza vaccination with rates of vaccination associated with the tetanus , diphtheria , and pertussis ( tdap ) vaccine that is written into all preprinted postpartum orders .
a total of 201 of 246 ( 82% ) received the tdap vaccine ( 95% confidence interval : 76% to 86% ) .  
none of the demographic and reproductive characteristics were significantly related to the receipt of either the seasonal or the h1n1 vaccine .
this indicates that , in our health system , primary language , race / ethnicity , and even insurance status were not barriers to the receipt of the vaccine .
the only significant predictor in table 2 was receipt of the other influenza vaccinse , that is , receipt of the seasonal vaccine was predictive of a higher likelihood of receiving the h1n1 vaccine and vice versa .
  in our health system during the 2009 - 2010 influenza season , we found rates of vaccination of pregnant women of 54% for the seasonal influenza vaccine and 51% for the h1n1 vaccine . when restricted in a manner similar to a 10-state sample   ( births through march 12 , 2010 )
our rates were approximately 10% higher : seasonal vaccine coverage was 61% versus 51% and h1n1 coverage was 59% versus 47% .
this is notable since our population serves pregnant women who have been shown in previous studies to be less likely to receive the vaccine , those who are disadvantaged , that is , uninsured , nonwhite , less educated , and of low income [ 2022 ] .  
other studies have reported on vaccination coverage of pregnant women in the 2009 - 2010 pandemic influenza season , many of which rely on self - report . in the united states ,
a nationally representative phone survey found coverage rates of 32% for the seasonal vaccine and 46% for the h1n1 vaccine .
a study at a university hospital in denver , co , found higher coverage rates of 64% for the seasonal vaccine and 54% for the h1n1 vaccine . unlike our study , the denver study relied on self - report and demonstrated high rates of vaccination outside their health system , 15% for the seasonal vaccine and 29% for the h1n1 vaccine .
a high rate of h1n1 vaccine coverage ( 76% ) was achieved in a public hospital prenatal clinic in seattle , wa , using a system which included chart prompts and a vaccine registry .
the highest rates were reported at the massachusetts general hospital with coverage rates of 88% and 86% for the seasonal and the h1n1 vaccines , respectively .
their sample was restricted to 3 months of the influenza season ( january 2010 to march 2010 ) which could have raised these estimates as compared to other studies , since both vaccines were more readily available at that time .
a time difference might in part explain the lower coverage rates of the h1n1 vaccine ( 26% ) reported in one health system , maimonides medical center in brooklyn , ny , as the sample began shortly after the h1n1 vaccine was available ( time frame of november 12 to december 19 , 2009 ) .
rates of seasonal coverage were reported to be 30% in alberta , while for h1n1 the rates have been reported to be between 63% and 76% [ 29 , 30 ] . in france ,
rates of the h1n1 coverage of pregnant women were lower : 38% in a 3-hospital study in paris   and 22% using a national insurance database . another insurance database from australia
reported even lower estimated coverage rates of 10% for the h1n1 vaccine in pregnant women from october 2009 to january 2010 . with one exception ,
all of the rates are lower than the 80% coverage rates targeted by the national healthy people 2020 objectives for pregnant women .
however , most represent large increases over the prior year rates , which appear to be sustained with 49% pregnant women reporting being vaccinated during the 2010 - 2011 influenza season . in our health system
we achieved rates higher than nationally reported rates ; we attribute this to a comprehensive approach to influenza .
for example , we undertook many of the prevention strategies cited by goldfarb et al .   in their successful program .
our actions included standing orders   and awareness activities ,   both of which have been demonstrated to increase vaccination rates .
reasons for our rates being lower than the highest reported rates may have included not having chart prompts   or not making use of a vaccine registry .
furthermore , our system of prenatal care includes clinics spread over a large geographic area , making messaging and implementing programs challenging .
however , streamlining the order process as we have been able to do with the tdap vaccine suggests that even higher rates can be achieved .
it was based on chart review which indicates that we can be relatively certain of the lower limit of our vaccination rates .
it is possible that actual coverage rates may be higher , especially in view of the high rates of vaccination outside of the health system reported by fisher et al . .
however , not knowing the magnitude of the outside coverage in our population , we would not want to speculate on how much higher the  real  coverage rates would have been .
another advantage of the chart review methodology is that many of the studies rely on self - report , which may have been an issue in the 2009 to 2010 season when 2 vaccines were available .
our own experience with our population suggests this may have occurred , with a frequent response of , 
i already received the flu vaccine ,  when they had received only one of the recommended two vaccines . furthermore , many of the studies relying on self - report had substantial nonresponse rates of approximately 50% ; this included studies with high reported coverage rates or those that were nationally representative [ 23 , 25 , 27 ] .
a limitation of our study is that it represents the cumulative efforts of one health system caring for the underserved , as such these results may not be generalizable to other populations or health systems .
finally , we do not know which of our interventions impacted vaccination rates the most .  
our study has a number of implications . for other health systems it would appear that improved vaccination rates as compared to the national rates are possible , even for health systems that are safety - net systems that provide medical care to large numbers of underserved patients . our success with a population which usually experiences lower coverage rates  minorities , uninsured , and with limited english - speaking ability  could be a model for other systems .
taken with goldfarb 's study , we also believe a comprehensive approach might be a rational strategy to achieve high coverage rates . given initial reports of continued high rates in pregnant patients over the subsequent influenza season to this study , it will be interesting to see if high vaccination rates continue in this population .
finally , given that self - report might overestimate and chart review might underestimate coverage rates , it would be interesting to supplement chart review with self - report to further characterize this in our population .
moreover , self - report in such a study would assist in determining the upper limit achievable by segregating those who represent missed opportunities versus those who refuse the vaccine .   in summary , our public safety - net institution achieved influenza vaccine coverage rates , that were higher than those reported national samples by instituting a comprehensive strategy .
this could be due to not capturing vaccinations done outside our health system , not including certain interventions in our vaccination strategy such as chart prompts , and not including an order for influenza vaccination on all postpartum orders .
 the purpose of this study was to compare influenza vaccination rates of pregnant women in a public safety - net health system to national coverage rates during the 2009 - 2010 pandemic influenza season . 
 a chart review of a random sample of deliveries was undertaken to determine rates of coverage and predictors of vaccine coverage of women who obtained prenatal care and delivered in our health system . 
 rates were calculated from deliveries from when the vaccine was first available through april 30 , 2010 . 
 coverage rates were 54% for the seasonal influenza vaccine and 51% for the h1n1 vaccine . 
 race / ethnicity , insurance status and language spoken did not predict the receipt of either vaccine . when we included only births which occurred through march 12 , 2010 , as was done in a large population - based study , the rates were 61% and 59% , respectively . 
 our rates are about 10% higher than the rates reported in that study . 
 our comprehensive strategy for promoting vaccine coverage achieved higher vaccination rates in a safety - net health system , which serves groups historically less likely to be vaccinated , than those reported for the pregnant population at large . 
1. Introduction
2. Methods
3. Results 
4. Discussion