Written by Erin Gartner, CNN
Unfounded rumors about the effectiveness of so-called flu vaccine are sometimes the result of unsubstantiated claims made by sources who do not have the scientific background to back up their concerns. That’s one conclusion from a 2018 study from the National Institute of Allergy and Infectious Diseases (NIAID), which examined reports of vaccination failure among the most common childhood vaccines.
During the 2017-2018 flu season, a spike in vaccine non-adherence was particularly acute among the first-line treatments — the trivalent influenza vaccines (TIV), which provide protection against two types of influenza virus and the RSV. While non-adherence rates varied between the four main children’s vaccines (the other two being measles, mumps and rubella), the spike among TIV was higher than with any other, the study found.
The relationship between TIV and low or inconsistent vaccine use may be related to “low perceived vaccine efficacy,” the study found. Consistent non-adherence to any one or all of the four vaccines was independently associated with both high perceived vaccine efficacy and non-adherence. The hypothesis is that higher perceived vaccine efficacy helps people understand and understand why the vaccine is needed.
“People with high perceived vaccine efficacy may be more likely to explain against vaccine non-adherence: ‘if it’s not working right, then it’s not working well,’” said Anna Vaas, an epidemiologist and senior author of the study. “People may have more confidence in the recommended timing, dosage, duration and geographic exposures. And the increase in non-adherence relates to perceived lack of efficacy.”
Concerns about vaccine effectiveness can also motivate people to delay vaccination, potentially making it more difficult to provide protection. As a result, even with high vaccine effectiveness, persistent lack of vaccination rates can contribute to infectious disease outbreaks, according to the study, which was published June 30 in the journal The New England Journal of Medicine.
The non-adherence is a consistent problem
Common factors contributing to widespread vaccine non-adherence in the US include inadequate supplies of the vaccines, insufficient distribution in some parts of the country, complexity of obtaining the vaccine for vaccination, and societal reasons for not making vaccination a priority, according to the study.
More attention also needs to be paid to helping parents understand how the vaccine works, given that a sizable group of people — including adolescents and young adults — may have weak immune systems, said Julie Gerberding, former director of the NIAID and a senior author of the study.
“This is our generation’s leprosy,” Gerberding said, referring to the incidence of unvaccinated people, also known as undervaccinated, in high-risk settings. By recognizing that vaccines don’t always work, those using the vaccines can be better prepared to use them effectively and can even give them up if they don’t.
“There’s also some information out there that prompts people to delay vaccination. However, there has to be some case-management strategies because the impact of delaying vaccination can be quite different for different populations,” she said.
Source limitations
For the study, the authors used the Centers for Disease Control and Prevention’s National Immunization Survey to evaluate vaccine non-adherence by age group, along with Google Flu Trends, 2015 data from the Centers for Disease Control and Prevention’s Global Influenza Network and other source documents and a Google Flu Trends search to retrieve vaccine non-adherence reports, which involved average daily flu-related Google searches in the United States. The underlying data were collected between 2005 and 2010 and provided information on licensed and non-licensed pharmacies and mass vaccination events such as flu shot clinics, according to the study.
The authors acknowledged, however, that at least two of the data and sources were self-reported, could only be used to evaluate events occurring over multiple years, were far from comprehensive and did not adjust for the occurrence of flu or other vaccination events. The data also included reports from individual people who may have told multiple organizations, which made the sample more like a stratified population than a representative one.
According to the study, the absolute level of non-adherence for all kids age two and older in the 2015-2016 season was 45.8%, up from 38.4% the previous year.