There have been repeated reports of outbreaks of “vaccine-preventable disease” or VPDs across United States over the past few years. A new research letter was published this week in the JAMA Pediatrics. It was titled, “Association of Vaccine-Preventable Disease Incidence With Proposed State Vaccine Exemption Legislation.”
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Researchers wrote that over the last few years increasing number of parents are opting to exempt themselves from the mandatory school vaccination requirements. Some schools mandate vaccination at enrolment and legislation allows parents to exempt themselves from these rules. Children who have thus not been vaccinated are susceptible to VPDs and are also susceptible to spreading these infections among others who cannot be vaccinated.
Experts have said that some people cannot be vaccinated due to their suppressed immunity. This includes infants below 6 months of age, elderly and those with diseases that suppress the immunity. If 90 percent or more of the population is vaccinated against a disease, the non vaccinated individuals are protected by herd immunity. With the declining number of vaccinated children, the herd immunity is affected say experts.
The research letter states that there was a study in 2018 that showed that after a VPD outbreak such as whooping cough or pertussis, there was an increased public awareness regarding uptake of the vaccine. This led to a fall in number of cases. Further a direct response was found between a VPD outbreak and issuance of a legislation that mandated vaccination against that particular infection.
They attempted to see if the state legislation trends were and the incidence of VPDs were linked especially in case of “vaccine exemption laws”. For this study the team linked the state reported VPD outbreaks reported in the National Notifiable Diseases Surveillance System (NNDSS) along with proposed bills that could influence the uptake of vaccine exemption laws between 2011 and 2017. All reports between 2010 and 2016 were included in the study.
The diseases targeted were “diphtheria; Haemophilus influenzae serotype B; hepatitis A and B; influenza; pneumococcal disease; measles; meningococcal disease serotypes A, B, C, Y, and W-135; mumps; pertussis; rubella and congenital rubella syndrome; tetanus; and varicella”. The Advisory Committee on Immunization Practices childhood schedule helped decide on these diseases. Each of these VPDs (outbreaks standardized as per 100 000 population) were correlated with the legislations that came up after the outbreaks. These legislations included bills that allowed more people to take up the vaccine or bills that restricted the exemptions option of parents from mandatory school entry vaccination. The team wrote, “Analyses were stratified by proposed bills that would (1) expand vaccine exemptions and (2) restrict vaccine exemptions.”
Results showed that for each of the states showed an average of 25 VPDs per 100,000 people per year during the study period. Further as a result of these outbreaks there were 175 bills that dealt with vaccine exemption and of these 53 percent or 92 bills increased the exemptions for the population while 47 percent or 83 bills dealt with taking away or restricting the exemptions for parents vaccinating their children.
On analysis the team noted that with each 1 Standard Deviation increase in the VPDs per 100 000 people, there was a 54 percent rise in the proposed bills. Looking at the association of expansions of exemptions and VPDs, no significant association was noted. On the other hand whooping cough outbreaks gave rise to bills that restricted exemptions.
The authors wrote, “This study revealed an association between reported VPDs and proposed state legislation that would alter vaccine exemption law.” The team added that rise in VPDs “were associated with an increase in bills that would restrict vaccine exemptions.” They explained this phenomenon saying that as the VPD outbreaks took place there was more media coverage that led to public awareness and also raised advocacy and this prompted the legislation.
The team also accepted some of the limitations of their study saying that there may be vaccine failures and also that they did not include the 2019 measles outbreaks in this study. This latest outbreak in New York, wrote the researchers, was responsible for removal of vaccine exemption from schools for reasons other than medically certified ones. This meant that parents who did not have a medical reason for not vaccinating their children would have to vaccinate them before they started school.
The authors of the study concluded that state legislation makers are more likely to introduce bills to reduce the vaccine exemptions for non medical reasons. They wrote in conclusion, “This is promising in light of increasing vaccine hesitancy and misinformation about childhood vaccinations.”
Goldstein ND, Purtle J, Suder JS. Association of Vaccine-Preventable Disease Incidence With Proposed State Vaccine Exemption Legislation. JAMA Pediatr. Published online November 18, 2019. doi: https://doi.org/10.1001/jamapediatrics.2019.4365