Does influenza vaccination exacerbate asthma?

Asthma prevalence and exacerbations in children: is there an association with childhood vaccination?

Infections and vaccinations may have a potential role in the normal maturation of the immune system, in the development and balance of regulatory pathways, and in the development and exacerbations of asthma. Asthma exacerbations often result from respiratory viral infections, and, while vaccination towards common viral infections may reduce the occurrence of such exacerbations, there has been concern that vaccinations can increase the risk of asthma. Current studies show that childhood vaccines, including inactivated influenza vaccine, are generally safe. However, there is some concern regarding possible exacerbations in infants or children with frequent wheezing or persistent asthma who are given live-attenuated influenza vaccination. Although severe allergic adverse events attributable to vaccination are extremely rare, all serious allergic reactions should be further assessed to detect the likely causative vaccine component, such as egg protein or gelatin. The risks of not vaccinating children far outweigh the risks of allergy and asthma exacerbations. Therefore, childhood vaccination should remain an essential part of child health programs and should not be withheld, even from children with asthma or those predisposed to allergy.

Influenza vaccination in adults with asthma: safety of an inactivated trivalent influenza vaccine

Despite recommendations in most countries for giving inactivated influenza vaccine to people with asthma, only a minority currently receive it. One reason for low vaccine coverage has been concern that vaccination may induce exacerbations of asthma. In this randomized trial, 291 patients between 18 and 65 years of age received either an inactivated influenza vaccine followed 14 days later by a saline placebo or placebo followed by the vaccine. Each patient received 1 dose of vaccine and 1 dose of placebo. The percentage of patients reporting at least one asthma exacerbation within 14 days after injection was similar following vaccine or placebo (28.3% and 25.5%, respectively). The combined exacerbation rate during the first 14-day interval was higher (31.5%) than that during the second 14-day interval (22.4%, P = 0.0135), indicating that the occurrence of exacerbations was not likely to be related to the sequence of injections. The percentages of individuals with solicited systemic symptoms were 56.6% and 44.8% after vaccine or placebo injection, respectively. We conclude that influenza vaccination did not increase the incidence of asthma exacerbations compared to placebo in this study and the vaccine was well tolerated. The results thus support annual influenza vaccination in patients with asthma.

Influenza vaccine in patients with asthma

Influenza virus continues to be a major cause of respiratory infection and is an important contributor to morbidity and mortality in at-risk populations, including those with underlying pulmonary conditions such as asthma. Vaccination with inactivated influenza vaccine remains the most popular method in controlling influenza through prevention. Current guidelines recommend the administration of the influenza vaccine to all patients with asthma. However, a third or fewer of those patients with asthma are currently receiving this vaccine. In this review, the risk-versus-benefit of influenza vaccination in children and adults with asthma is evaluated, based on the current evidence.

Safety and efficacy of influenza vaccine in children

OBJECTIVE

To describe the safety and efficacy of influenza vaccines in asthmatic children.

DATA SOURCES

Literature was identified by a MEDLINE search (2002-March 2003). Key search terms included asthma, exacerbation, children, vaccine, and influenza.

DATA SYNTHESIS

Concerns that the influenza vaccine may exacerbate asthma attacks have kept many asthmatic children from receiving this immunization. Researchers have conducted studies to determine the burden of influenza on asthmatic children, the safety of influenza vaccines, and their benefit in the presence of glucocorticoid burst therapy in the same population.

CONCLUSIONS

Influenza vaccines tested are safe and efficacious in asthmatic children.

Potential burden of universal influenza vaccination of young children on visits to primary care practices

OBJECTIVE

To estimate the additional number of visits to primary care practices that would be required to deliver universal influenza vaccination to 6- to 23-month-old children.

METHODS

Children who were covered by commercial and Medicaid managed care plans (70% of children in the region; >8000 children in each of 3 consecutive influenza seasons) in the 6-county region surrounding and including Rochester, New York, were studied. An analysis was conducted of insurance claims for visits (well-child care [WCC]; all other visits) to primary care practices during 3 consecutive influenza vaccination seasons (1998-2001). We determined the proportion of children who made 1 or 2 visits during the potential influenza vaccination period, simulating several possible lengths of time available for influenza vaccination (2, 3, 4, or 5 months). We measured the proportion of children who were vaccinated during each influenza vaccination period. The added visit burden was defined as the number of additional visits that would be required to vaccinate all children, simulating 2 scenarios: 1) administering influenza vaccination only during WCC visits and 2) considering all visits as opportunities for influenza vaccination.

RESULTS

Results were similar for each influenza season. Considering a 3-month influenza vaccination window and assuming that no opportunities were missed, if only WCC visits were used for influenza vaccination, then 74% of 6- to 23-month-olds would require at least 1 additional visit for vaccination--39% would require 1 additional visit and 35% would require 2 additional visits. If all visits to the practice were used for influenza vaccination during the 3-month window, then 46% would require at least 1 additional visit--34% would require 1 additional visit and 12% would require 2 additional visits. Longer vaccination periods would require fewer additional visits; eg, if a 4-month period were available, then 54% of children would require 1 or 2 additional visits if only WCC visits were used and 29% would require 1 or 2 additional visits if all visits were used for influenza vaccinations. Younger children (eg, 6- to 11-month-olds) would require fewer additional visits than older children (12- to 23-month-olds) because younger children already have more visits to primary care practices.

CONCLUSIONS

Implementation of universal influenza vaccination will result in a substantial increased burden to primary care practices in terms of additional visits for influenza vaccination. Practice-level strategies to minimize the additional burden include 1) using all visits (not just WCC visits) as opportunities for vaccination, 2) providing influenza vaccination for the maximum possible time period by starting to vaccinate as early as possible and continuing to vaccinate as late as possible, and 3) implementing short and efficient vaccination-only visits to accommodate the many additional visits to the practice.

Challenges and controversies in immunization safety

No vaccine is perfectly safe or effective. As diseases such as diphtheria and polio fade, vaccine safety concerns, especially alleged links between vaccinations and several chronic illnesses, have become increasingly prominent in the media and to the public. This article reviews the current scientific evidence on several recent vaccine safety controversies. It also provides information on how various safety research is conducted, some of the concurrent challenges, and finally, some guidance on communicating with patients on vaccine risks.

The burden of influenza illness in children with asthma and other chronic medical conditions

OBJECTIVE

Although influenza immunization is recommended for children with high-risk medical conditions, the majority of such children do not receive influenza vaccine. This study was designed to measure the burden of influenza among children with asthma and other chronic medical conditions.

STUDY DESIGN

We performed a retrospective cohort study of children younger than 15 years with medically treated asthma or other chronic medical conditions enrolled in the Tennessee Medicaid program from 1973 to 1993. We determined rates of hospitalization for acute cardiopulmonary disease, outpatient visits, and antibiotic courses throughout the year. Annual differences between event rates when influenza virus was circulating and event rates during winter months when there was no influenza in the community were used to calculate influenza-attributable morbidity.

RESULTS

Influenza accounted for an average of 19, 8, and 2 excess hospitalizations for cardiopulmonary disease yearly per 1000 high-risk children aged <1 year, 1 to <3 years, and 3 to <15 years, respectively. For every 1000 children, an estimated 120 to 200 outpatient visits and 65 to 140 antibiotic courses were attributable to influenza annually.

CONCLUSIONS

Children younger than 15 years with asthma and other chronic medical conditions experience substantial morbidity requiring inpatient and outpatient care during influenza season. More effective targeting of this population for annual influenza immunization is warranted.

Influenza and respiratory syncytial virus. Update on infection, management, and prevention

This article is an overview of the epidemiology and spectrum of clinical disease attributed to influenza and respiratory syncytial virus in children. It separately discusses the pathogenesis of the two diseases and the host responses to the viruses to emphasize each infection's significance and need for a vaccine. Updates on current preventive measures and a preview of potential future vaccine developments are presented.

Respiratory viruses and asthma

Viral infections have become increasingly recognized as a significant cause of asthma exacerbations, mainly because of improved viral detection techniques. Unfortunately, the ability to specifically treat viral infections and to limit the asthma morbidity associated with these agents has not kept pace with diagnostic technology. This article focuses on current concepts of the epidemiology of viruses in asthma exacerbations, investigations studying the physiologic and immunologic consequences of viral infection, and potential therapies to minimize virally-induced airway hyperresponsiveness. To impact this significant health problem, researchers must definitively ascertain the mechanisms by which viruses induce airway reactivity and must develop rational, safe approaches to prevent the consequences of viral infection in the patient with asthma.