And in three-quarters of those cases, parents intentionally didn’t get their children vaccinated because of philosophical or religious reasons.
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Measles – a disease that was completely eliminated in the United States 15 years ago – has captured national attention recently, thanks to outbreaks among unvaccinated travelers who have contracted the disease overseas. “Strategies aimed at decreasing vaccine refusal may have an important impact on the community”. They found that of the 1,416 measles cases reported in the USA during that time span, 804 cases, or 56.8 per cent, had no medical history or record of receiving the vaccine, as opposed to the 199 cases, or 14.1 per cent, involving individuals who did.
“Outbreaks of diseases like measles and pertussis remind us that there are still ways to improve how we use vaccines to safeguard the health of children and adults across the United States”, he said. When a certain percent of a population is vaccinated, it helps protect even those who can’t be immunized, because it contains the infection. At the same time, anti-vaccination sentiments have found footing among some parents anxious over unfounded safety concerns.
The study points to a 2014 outbreak of measles that originated at Disneyland in Anaheim, Calif. Researchers linked refusing vaccination to a higher risk for measles and pertussis, even among those who had been previously vaccinated.
“Fundamental to the strength and legitimacy of justifications to override parental decisions to refuse a vaccine for their child is a clear demonstration that the risks and harms to the child of remaining unimmunized are substantial”, they wrote.
Since measles was declared eliminated in 2000, over half of its cases reported in the US were for those without history of measles vaccination. When a growing slice of a given population declines to be vaccinated against a disease, the likelihood that there will be an outbreak of that disease increases.
In an analysis published Tuesday in the Journal of the American Medical Assn., epidemiologists scoured reports of measles and pertussis outbreaks to glean what role vaccination refusal and hesitance played.
States require childhood vaccinations through public school admission, with some of them tightening laws on vaccination exemptions.
The case with pertussis, however, also revealed situations where epidemics occurred in regions with high pertussis vaccination rates, which the authors attribute to waning immunity in the population.
“If you wait until a child is two or three to start the immunization series that leaves that child unprotected in their early childhood and that’s when they are most at risk of getting sick from a vaccine-preventable disease”, said Dr. Schulte. Of those cases, 71 percent of people had religious or philosophical exemptions, rather than medical reasons to skip vaccinations.
Researchers reviewed 32 reports of pertussis outbreaks in which the vaccination status of the 10,069 patients was known. The age range was 10 days to 87 years of age.
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Strategies to reduce vaccine refusal include making it harder to obtain a vaccine exemption, and addressing the reasons for parents’ hesitancy to vaccinate their children, the researchers said. And among those children that had been vaccinated, 11 percent were infected from an unvaccinated source. In some cases, the disease can develop into a potentially fatal meningitis.
