Robert A. Bednarczyk

Association Between Vaccine Refusal and Vaccine-Preventable Diseases in the United States: A Review of Measles and Pertussis

IMPORTANCE Parents hesitant to vaccinate their children may delay routine immunizations or seek exemptions from state vaccine mandates. Recent outbreaks of vaccine-preventable diseases in the United States have drawn attention to this phenomenon. Improved understanding of the association between vaccine refusal and the epidemiology of these diseases is needed. OBJECTIVE To review the published literature to evaluate the association between vaccine delay, refusal, or exemption and the epidemiology of measles and pertussis, 2 vaccine-preventable diseases with recent US outbreaks. EVIDENCE REVIEW Search of PubMed through November 30, 2015, for reports of US measles outbreaks that have occurred since measles was declared eliminated in the United States (after January 1, 2000), endemic and epidemic pertussis since the lowest point in US pertussis incidence (after January 1, 1977), and for studies that assessed disease risk in the context of vaccine delay or exemption. FINDINGS We identified 18 published measles studies (9 annual summaries and 9 outbreak reports), which described 1416 measles cases (individual age range, 2 weeks-84 years; 178 cases younger than 12 months) and more than half (56.8%) had no history of measles vaccination. Of the 970 measles cases with detailed vaccination data, 574 cases were unvaccinated despite being vaccine eligible and 405 (70.6%) of these had nonmedical exemptions (eg, exemptions for religious or philosophical reasons, as opposed to medical contraindications; 41.8% of total). Among 32 reports of pertussis outbreaks, which included 10,609 individuals for whom vaccination status was reported (age range, 10 days-87 years), the 5 largest statewide epidemics had substantial proportions (range, 24%-45%) of unvaccinated or undervaccinated individuals. However, several pertussis outbreaks also occurred in highly vaccinated populations, indicating waning immunity. Nine reports (describing 12 outbreaks) provided detailed vaccination data on unimmunized cases; among 8 of these outbreaks from 59% through 93% of unvaccinated individuals were intentionally unvaccinated. CONCLUSIONS AND RELEVANCE A substantial proportion of the US measles cases in the era after elimination were intentionally unvaccinated. The phenomenon of vaccine refusal was associated with an increased risk for measles among people who refuse vaccines and among fully vaccinated individuals. Although pertussis resurgence has been attributed to waning immunity and other factors, vaccine refusal was still associated with an increased risk for pertussis in some populations.

Parents' Source of Vaccine Information and Impact on Vaccine Attitudes, Beliefs, and Nonmedical Exemptions

In recent years, use of the Internet to obtain vaccine information has increased. Historical data are necessary to evaluate current vaccine information seeking trends in context. Between 2002 and 2003, surveys were mailed to 1,630 parents of fully vaccinated children and 815 parents of children with at least one vaccine exemption; 56.1% responded. Respondents were asked about their vaccine information sources, perceptions of these sources accuracy, and their beliefs about vaccination. Parents who did not view their childs healthcare provider as a reliable vaccine information source were more likely to obtain vaccine information using the Internet. Parents who were younger, more highly educated, and opposed to school immunization requirements were more likely than their counterparts to use the Internet for vaccine information. Compared to parents who did not use the Internet for vaccine information, those who sought vaccine information on the Internet were more likely to have lower perceptions of vaccine safety (adjusted odds ratio (aOR), 1.66; 95% CI, 1.18–2.35), vaccine effectiveness (aOR, 1.83; 95% CI, 1.32–2.53), and disease susceptibility (aOR, 2.08; 95% CI, 1.49–2.90) and were more likely to have a child with a nonmedical exemption (aOR 3.53, 95% CI, 2.61–4.76). These findings provide context to interpret recent vaccine information seeking research.

Association of Tdap Vaccination With Acute Events and Adverse Birth Outcomes Among Pregnant Women With Prior Tetanus-Containing Immunizations

IMPORTANCE The Advisory Committee on Immunization Practices (ACIP) recommends the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine for pregnant women during each pregnancy, regardless of prior immunization status. However, safety data on repeated Tdap vaccination in pregnancy is lacking. OBJECTIVE To determine whether receipt of Tdap vaccine during pregnancy administered in close intervals from prior tetanus-containing vaccinations is associated with acute adverse events in mothers and adverse birth outcomes in neonates. DESIGN, SETTING, AND PARTICIPANTS A retrospective cohort study in 29,155 pregnant women aged 14 through 49 years from January 1, 2007, through November 15, 2013, using data from 7 Vaccine Safety Datalink sites in California, Colorado, Minnesota, Oregon, Washington, and Wisconsin. EXPOSURES Women who received Tdap in pregnancy following a prior tetanus-containing vaccine less than 2 years before, 2 to 5 years before, and more than 5 years before. MAIN OUTCOMES AND MEASURES Acute adverse events (fever, allergy, and local reactions) and adverse birth outcomes (small for gestational age, preterm delivery, and low birth weight) were evaluated. Women who were vaccinated with Tdap in pregnancy and had a prior tetanus-containing vaccine more than 5 years before served as controls. RESULTS There were no statistically significant differences in rates of medically attended acute adverse events or adverse birth outcomes related to timing since prior tetanus-containing vaccination. [table: see text]. CONCLUSIONS AND RELEVANCE Among women who received Tdap vaccination during pregnancy, there was no increased risk of acute adverse events or adverse birth outcomes for those who had been previously vaccinated less than 2 years before or 2 to 5 years before compared with those who had been vaccinated more than 5 years before. These findings suggest that relatively recent receipt of a prior tetanus-containing vaccination does not increase risk after Tdap vaccination in pregnancy.

Risk of anaphylaxis after vaccination in children and adults

BACKGROUND Anaphylaxis is a potentially life-threatening allergic reaction. The risk of anaphylaxis after vaccination has not been well described in adults or with newer vaccines in children. OBJECTIVE We sought to estimate the incidence of anaphylaxis after vaccines and describe the demographic and clinical characteristics of confirmed cases of anaphylaxis. METHODS Using health care data from the Vaccine Safety Datalink, we determined rates of anaphylaxis after vaccination in children and adults. We first identified all patients with a vaccination record from January 2009 through December 2011 and used diagnostic and procedure codes to identify potential anaphylaxis cases. Medical records of potential cases were reviewed. Confirmed cases met the Brighton Collaboration definition for anaphylaxis and had to be determined to be vaccine triggered. We calculated the incidence of anaphylaxis after all vaccines combined and for selected individual vaccines. RESULTS We identified 33 confirmed vaccine-triggered anaphylaxis cases that occurred after 25,173,965 vaccine doses. The rate of anaphylaxis was 1.31 (95% CI, 0.90-1.84) per million vaccine doses. The incidence did not vary significantly by age, and there was a nonsignificant female predominance. Vaccine-specific rates included 1.35 (95% CI, 0.65-2.47) per million doses for inactivated trivalent influenza vaccine (10 cases, 7,434,628 doses given alone) and 1.83 (95% CI, 0.22-6.63) per million doses for inactivated monovalent influenza vaccine (2 cases, 1,090,279 doses given alone). The onset of symptoms among cases was within 30 minutes (8 cases), 30 to less than 120 minutes (8 cases), 2 to less than 4 hours (10 cases), 4 to 8 hours (2 cases), the next day (1 case), and not documented (4 cases). CONCLUSION Anaphylaxis after vaccination is rare in all age groups. Despite its rarity, anaphylaxis is a potentially life-threatening medical emergency that vaccine providers need to be prepared to treat.

Impact of Statins on Influenza Vaccine Effectiveness Against Medically Attended Acute Respiratory Illness

BACKGROUND Statins have antiinflammatory effects that may impact vaccine-induced immune responses. We investigated the impact of statin therapy on influenza vaccine effectiveness (VE) against medically attended acute respiratory illness (MAARI). METHODS We conducted a retrospective cohort study over nine influenza seasons using research databases of a large managed care organization in the United States. Influenza vaccination and statin prescription statuses of cohort members and MAARI cases were ascertained on a per-season basis. Incidence rate ratios (IRRs) of MAARI were estimated using Poisson regression and stratified by statin use. Using a ratio of ratios approach, we compared IRRs from periods during to IRRs from periods before influenza circulation and then used relative IRRs to compute VE. RESULTS After adjustment for multiple prespecified covariates, the influenza VE against MAARI was lower among statin users than nonusers during periods of local (14.1% vs 22.9%; mean difference, 11.4%; 95% confidence interval [CI], -1.7% to 26.1%) and widespread (12.6% vs 26.2%; mean difference, 18.4%; 95% CI, 2.9%-36.2%) influenza circulation. CONCLUSIONS In this study, statin therapy was associated with reduced influenza VE against MAARI. Since many cases of MAARI are not caused by influenza, studies of the impact of statins on influenza VE against laboratory-confirmed influenza are needed.

Vaccinating My Way—Use of Alternative Vaccination Schedules in New York State

OBJECTIVE To identify children vaccinated following an alternative vaccine schedule using immunization information system data and determine the impact of alternative schedule use on vaccine coverage. STUDY DESIGN Children born in New York State, outside New York City, between January 1, 2009 and August 14, 2011 were assessed for vaccination patterns consistent with use of an alternative schedule. Children who by 9 months of age had at least 3 vaccination visits recorded in the statewide mandatory immunization information system after 41 days of age were classified as either attempting to conform to the Centers for Disease Control and Prevention published recommended vaccination schedule or an alternative schedule. The number of vaccination visits and up-to-date status at age 9 months were compared between groups. RESULTS Of the 222 628 children studied, the proportion of children following an alternative schedule was 25%. These children were significantly less likely to be up-to-date at age 9 months (15%) compared with those conforming to the routine schedule (90%, P < .05). Children following an alternative schedule on average had about 2 extra vaccine visits compared with children following a routine schedule (P < .05). CONCLUSIONS Almost 1 in 4 children in this study appear to be intentionally deviating from the routine schedule. Intentional deviation leads to poor vaccination coverage leaving children vulnerable to infection and increasing the potential for vaccine-preventable disease outbreaks.

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

BACKGROUND To 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. METHODS Using 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. RESULTS Overall 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. CONCLUSIONS In 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.

Reducing financial barriers to vaccinating children and adolescents in the USA.

Purpose of review To increase awareness of the financial barriers to childhood and adolescent vaccination, recent steps taken to mitigate these barriers, and remaining gaps following passage of Federal healthcare reform legislation. Recent findings Financial barriers to vaccination remain, even with the safety net of the Vaccines for Children Program. Newly recommended vaccines have substantially increased the cost to fully vaccinate a child up to age 18 years, and the combination of these cost burdens and inadequate reimbursement, in both the private and public sectors, has led some physicians to seriously consider stopping vaccination services. Up to 20% of privately insured children or adolescents have coverage that does not fully cover all costs of immunization, potentially leading to fragmented and inadequate preventive care. Summary Federal healthcare reform legislation, as currently constituted, may not fully address all financing gaps, and the extent to which financial barriers to immunization services remain will need to be evaluated as the legislation is implemented. Recent National Vaccine Advisory Committee recommendations need to be considered to address financial barriers to immunization.

Benefits to mother and child of influenza vaccination during pregnancy

Influenza virus infection contributes to substantial morbidity and mortality globally. Included in the list of groups at higher risk of either influenza infection or severe complications following influenza infection are pregnant women and their newborns. Influenza vaccination offers a safe and effective means to prevent or lessen the severity of influenza infections. Recent research has helped elucidate the impact of influenza infection and vaccination on pregnant women and their newborn children and young infants. This review summarizes recent findings in this area and identifies additional gaps in the evidence base that need to be addressed to appropriately inform vaccination policies worldwide, to protect pregnant women and their children from influenza and related complications.

Affluence as a predictor of vaccine refusal and underimmunization in California private kindergartens

BACKGROUND Non-medical vaccine exemption rates in California private schools far exceed those of public schools, but little is known about specific factors which may be associated with high exemption rates in private schools. METHODS The percent of personal-belief exemptions (PBEs) among California public and private kindergartens were computed for 2000-2001 to 2014-2015 academic years. For the 2014-2015 academic year, a random sample of private schools was selected to investigate associations between kindergarten characteristics (tuition amount, religious affiliation) and vaccine profile (non-medical vaccine exemptions, vaccine coverage). RESULTS The proportion of private kindergartens reporting 5% or more children with PBEs increased from 9% (2000-2001) to 34% (2013-2014), followed by a small decrease in 2014-2015 (31%). Overall, 93.7% (565/605) of kindergartens sampled in 2014-2015 had data available. Very high PBE levels (>20%) were seen among secular and non-Catholic, Christian kindergartens but not Roman Catholic, Jewish or Islamic kindergartens. However, the majority of schools at all tuition levels had fewer than 5% of children with a PBE. Kindergartens with an annual tuition of