How vaccines hinder disease spread
http://www.cidrap.umn.edu/news-perspective/2019/11/skipping-measles-vaccine-tied-triple-risk-disease-spread
This article details the results of 16 years’ worth of data on reported measles cases and disease susceptibility, finding that unvaccinated people are three to four times more infectious than those with measles who have been vaccinated. Over 2,000 cases, ranging from 2001 to 2017, were analyzed in the study. Analysis showed that effective reproductive number (R), which measures transmissibility, is significantly higher for unvaccinated patients (.76 for no vaccine doses, .17 for one does, .27 for 2+). Out of 23 possible “superspreading events,” 19 of the superspreaders were unvaccinated. As the measles vaccine is highly effective (93-97%), doctors attribute higher measles transmission to lack of vaccination rather than ineffective vaccination.
As we’ve discussed in class, disease transmission is directly related to R, and R can be reduced by lowering either k, the number of contacts, or p, transmission probability. From the study, in areas with similar characteristics and k values, unvaccinated patients saw much higher R’s. This is due to an increased p due to a lack of vaccination. The measles vaccine reduces the likelihood of transmission, therefore reducing R, and has a significant influence on whether or not a person catches the disease. To prevent superspreading events, to protect oneself, and to protect the community, the majority of people in susceptible communities should be vaccinated for measles.