February 12, 2024
Heads up
(This has turned into a more complicated post than I anticipated, so I’m breaking it into two sections. Expect the other half tomorrow. The first is a reminder about the infectiousness and dangers of measles. The second will be about herd immunity, why some vaccines work better than others, and how lower vaccination rates increase risks.)
In case you haven’t heard, measles cases are popping up across the US. It’s even worse in Europe where they had more than 42,000 (!!) cases last year, more than 40 times the levels of 2022. Partly because of lack of routine vaccinations in countries like Kazakhstan where infants missed routine vaccines during the pandemic and also because of vaccine hesitancy. The UK is worried that an outbreak there will spread with deadly consequences. Uptake of MMR vaccine dropped from 96% in 2019 to 93% across Europe. Which doesn’t sound like a big drop but the threshold for herd immunity in measles is 95%. International travel risks spreading the outbreaks further. Most outbreaks in the US are related to travel exposures.
We know why measles is becoming an issue again: vaccine hesitancy, along with missed routine vaccinations during the pandemic. The World Health Organization was worried about measles outbreaks when they saw delays of vaccinations 2 years ago.
Let’s start with a reminder of the basic reproduction number or R Nought (R0). We learned about this early in our pandemic. The R0 is the number of secondary infections that will be caused by each individual infection. In the beginning, SARS-CoV-2 had an R0 of about 2.6. Debate is ongoing about the R0’s of the new variants. If an infection has an R0 <1, it will die out, transmission will be rare.
Measles is the most infectious virus known with an R0 between 12-18. That means each case will pass on the infection to 12-18 people in a susceptible (unexposed, un-immunized) population. This 15 or so will then pass it on to another 15 or so. Truly exponential growth. People born before 1957 are assumed to have had it and most everyone else has been immunized since, making measles infections rarer, because the population has high immunity. That’s what herd immunity is.
The MMR vaccine has been effective. If someone’s vaccinated, their risk of measles is 35 times less likely than someone without immunity. (95% of people are fully protected after they get their second dose.)
Most people under the age of 65 have never seen a case of measles. Some social media sites and the anti-vaccine movement may lead you to believe that measles is a mild childhood illness with minimal consequences. For some that’s true, they recover well. But for others it can be devastating: pneumonia, ear infections, hospitalizations, encephalitis, deaths. A big cause of deafness in children.
Others pass on disinformation about the dangers of the vaccine. It has been repeatedly shown not to cause autism. The original studies were withdrawn and shown to be fraudulent.
This image from the New York Times illustrates the dangers of that misinformation.
(Source: New York Times)
But nothing is perfect. A breakthrough case is rare but possible (3 out of 100 fully vaccinated people will get infected). The disease does tend to be milder in those vaccinated.
Another rare complication from measles is that it seems to harm the developing immune system of children. The weakened immune system leaves the child vulnerable to other infections for years. The virus kills the cells that make the antibodies. It can increase mortality in children from other infectious diseases.
Good reasons to encourage vaccinations.
Tomorrow more about that.
For now, let’s celebrate Flaco.
“Flaco is free, like all birds should be,” said Philippe Petit, a high-wire artist.
Flaco, the Eurasian Eagle-Owl that was released from the Central Park Zoo a year ago, is still free. Born and reared in captivity, his cage was cut open and he escaped. Because of concern for his well-being, there were calls to capture him. But he surprised everyone. He started catching rats and other critters in Central Park. The authorities continue to monitor him for distress, but feel he is surviving well. He is perhaps lonely, but free. Able to hunt his own food. Travel around the city, see the sights. They still don’t know who cut open his cage.
And finally, my caveat is that this is my experience and my opinions, which are subject to change as more information is available. Thanks for reading.
Share this post if you know of others who may be interested. All links are listed at the bottom of this post. The New York Times articles have links that are gift links, allowing you to read the article for free.
https://www.nytimes.com/2024/02/02/nyregion/flaco-owl-central-park-zoo.html?unlocked_article_code=1.Uk0.tS-T.Bu-cmT78aUiJ&smid=url-share
https://www.nbcnews.com/health/health-news/measles-outbreaks-anti-vaccine-misinformation-rcna136994
https://unric.org/en/who-alarming-rise-of-measles-cases-in-europe/
https://www.nytimes.com/2024/01/24/health/measles-europe.html?unlocked_article_code=1.Uk0.VfY-.lNXUZJZTqZz7&smid=url-share
https://www.bmj.com/content/369/bmj.m1891
https://www.usatoday.com/story/news/health/2024/02/07/measles-cases-us-states-map/72507771007/
https://www.healthline.com/health/r-naught-reproduction-number#meaning
https://www.who.int/news/item/15-07-2022-covid-19-pandemic-fuels-largest-continued-backslide-in-vaccinations-in-three-decades
https://www.bbc.com/news/health-68068226
https://www.medpagetoday.com/infectiousdisease/vaccines/108434 measles
https://www.usatoday.com/story/news/health/2024/01/26/cdc-issues-alert-measles-global/72365871007/
https://www.science.org/doi/10.1126/science.aaa3662?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
https://www.nytimes.com/2019/10/31/health/measles-vaccine-immune-system.html