The Measles Blame Game

I really hate measles. I know, I know…

There have been 3 measles outbreaks (defined as more than 3 cases related cases) so far this year. Historically that isn’t really a lot, but the outbreak in Texas right now is approaching 150 cases, which is a lot for a single outbreak. It has also resulted in the first confirmed measles death in the US since 2015.

There are some attacks on RFK Jr that his outspoken position as a vaccine critic has driven people to eschew the MMR vaccine, thus escalating the risk for children to contract and spread measles. While I think RFK’s advocacy in this realm is abhorrent, I also suspect it hasn’t been particularly effective.

But before we discuss blame, I want to contextualize the current situation.

Measles is an Imported Disease

Measles has been eradicated in the United States. That means that we have a vaccination rate high enough that it cannot spread indefinitely in our population. When there are measles outbreaks in the US, they are coming into the country from an outside source, they spread a bit, and then they peter out due to a lack of infectable targets.

In 2018 there were 17 measles outbreaks and 97% of the cases were directly connected to international travel. 70% were from US residents who contracted the disease abroad and then came home and 30% were from foreign visitors. This isn’t really a vaccination problem, it’s just the nature of a highly contagious disease and a world of quick and smooth international travel.

When measles comes to the United States, it can flare up into an “outbreak” (as few as 3 cases) but it rarely spreads far due to our robust vaccination rates and our ability to identify and isolate cases.

When measles does spread in the US, it is frequently due to a confluences of factors involving tight communities with low vaccination rates. This is because…

Measles Is A Community Disease

Measles is incredibly contagious, almost uniquely so. Infectious diseases are given an “R₀“, which describes how quickly a disease can spread. R₀“ is pretty simple, it describes how many people an infected person is likely to spread the disease to. The R₀“ for Covid is 1.5-3.5 which means they expect an infected persons to spread it to two to three other people. The R₀“ for measles is 12-18, which is a wildfire spread.

The last really big year for measles was 2019, when there were 1,249 confirmed cases. The stats for these cases are striking. Eight outbreaks and 85% of all cases were in “underimmunized, close-knit communities”, mostly in Orthodox Jewish communities in New York.

Vaccines Stop Measles

Measles is a disease where the case for vaccination is clear as day. It’s a disease that has disproportionate impact on children (44% of cases in 2019 were in children under 5) and vaccination is enormously effective. The MMR vaccination rate in the US is over 90% but that small group of unvaccinated population represent 70-85% of measles cases.