Many commentators have recently written and said that members of the migrant caravan and Central American immigrants in general are diseased. Former Immigration and Customs Enforcement agent David Ward claimed that the migrants are “coming in with diseases such as smallpox,” a disease that the World Health Organization (WHO) certified as being eradicated in 1980. One hopes Mr. Ward was more careful in enforcing American immigration law than in spreading rumors that migrants are carrying one of the deadliest diseases in human history nearly 40 years after it was eradicated from the human population. But even on other diseases, Ward and others do not have a compelling argument.
WHO has national estimates of vaccination coverage rates by country and type of vaccine. It’s unclear whether vaccination coverage rates include immigrants, but they definitely include those born in each country as of 2017. Vaccination coverage rates for the United States were unavailable for Tuberculosis and one of the polio vaccines (IPV1) while the IPV1 vaccine coverage rate is also unavailable for Costa Rica. We shouldn’t expect vaccination rates to be the same in all countries for at least two reasons. First, some diseases are more prevalent in certain climates so the requirement for vaccination there can be lower or higher. Second, vaccines have a positive externality so there is less of an individual incentive to become vaccinated as all of the benefits are not internalized to the individual who receives the shot. I expect the first reason to be more important than the second as enough benefits are internalized for the net-benefit of a vaccine to be positive (yes, vaccines are great) while many of the governments in these countries strongly encourage or mandate vaccination.
Figure 1 shows that average vaccination rates for Tuberculosis (BCG), Diphtheria, Pertussis, & Tetanus (DTP1), Diphtheria, Pertussis, & Tetanus (DTP3), Hepatitis B (HepB_BD), Hepatitis B (HepB3), Haemophilus Influenzae (Hib3), Polio (IPV1), Measles 1st Dose (MCV1), Measles 2nd Dose (MCV2), Streptococcus Pneumoniae (PCV3), Polio (Pol3), Rubella (RCV1), and Rotavirus (RotaC). The United States is in the middle of the pack with an 89 percent average vaccination coverage rate.
The following figures all show the vaccination coverage rates for different vaccines in Central American countries relative to the United States. In some figures, some countries are excluded because there are no WHO estimates of their vaccination rates. The United States does not have the highest vaccination coverage rate for any vaccine reported below. Perhaps members of the migrant caravan have lower vaccination rates than their fellow countrymen or they are carrying other serious contagions that cannot be vaccinated against. But for most of these illnesses below, you have more to fear from your fellow Americans than from Central Americans.