Is a Vaccine Strain Causing The Latest Measles Outbreak?

What’s the first question anti-vaccine folks start asking whenever we see a large outbreak of measles?

No, it’s not how can I get my kids vaccinated and protected so that they don’t get measles…

It is whether or not it a vaccine strain of measles started the outbreak.

Where do folks get all of this stuff about genotypes and vaccine strains? I wonder…

Yup.

The usual suspects.

Is a Vaccine Strain Causing The Latest Measles Outbreak?

Why do folks who intentionally don’t vaccinate their kids desperately want these measles outbreaks to be caused by a vaccine strain?

Because then it isn’t their fault that their kids are at risk of getting a life-threatening disease!

It’s never a vaccine strain though.

Remember the Disneyland measles outbreak. A lot of folks were talking about vaccine strains when it first started.

“…California patients were genotyped; all were measles genotype B3, which has caused a large outbreak recently in the Philippines…”

Measles Outbreak — California, Dec 2014–Feb 2015

It wasn’t a vaccine strain.

Outbreaks	Year	Genotype
Minnesota	2017	B3
Tennessee	2016	B3
California	2015	B3
Florida	2013	D8
California	2014	B3, D8
Brooklyn	2013	D8
North Carolina	2013	D8
Minnesota	2011	B3
Washington, Illinois	2008	D5, D4

For example, during 2011, 222 cases of measles and 17 outbreaks were reported in the United States, with most cases originating from just five countries (France, Italy, Romania, Spain, and Germany). Six different genotypes were identified, including B3, D4, G3, D8, H1, and D9. No vaccine strains…

And no, it doesn’t matter that the vaccine strain of measles, genotype A, differs from all of the wild strains of measles we see in the outbreaks.

“Vaccine induced immunity protects against all virus strains. Measles is considered a monotypic virus despite the genetic variations.”

Factsheet about measles

Unlike the flu, HPV, and pneumococcal bacteria, in which vaccines only protect against different serotypes, in the case of measles, the genotype simply helps us figure out where the measles case came from.

And no, the latest outbreak, wherever it is, wasn’t caused by shedding from a vaccine.

But if it isn’t the vaccine strain, then why do they that is it important to rapidly identify wild strains vs vaccine strains?

“During measles outbreaks, it is important to be able to rapidly distinguish between measles cases and vaccine reactions to avoid unnecessary outbreak response measures such as case isolation and contact investigations.”

Roy et al on Rapid Identification of Measles Virus Vaccine Genotype by Real-Time PCR

That’s easy to answer.

Outbreaks typically trigger a lot of folks to get vaccinated. While that’s great, one possible problem is that some of those folks might develop a fever and/or rash after their MMR vaccine. So it is important to quickly figure out whether they are part of the outbreak and have a wild strain (maybe they were exposed before their vaccine could start to work) or are having a common, mild vaccine reaction.

But couldn’t they have vaccine-associated measles if they have a rash and fever and a vaccine strain? Theoretically, but then they would likely have true measles symptoms. And even in these rare case reports, the children didn’t spread the measles to anyone else.

So why are you waiting to know the genotype of the measles strain causing the outbreak in your area? Hopefully, it isn’t to help you decide whether or not to vaccinate and protect your kids. While it is interesting to know where the outbreak originated, you can bet that it isn’t a vaccine strain.

More on Vaccine Strains Causing Measles Outbreaks

• VAXOPEDIA – Measles Vaccines vs Measles Strains
• VAXOPEDIA – Can MMR Shedding Start a Measles Outbreak?
• How I Accidentally Started an Anti-Vaxx Myth in the Name of Science
• Is the measles outbreak that occurred in Disney Land of a different strain than what’s in the vaccine?
• Genotypes, Serotypes and the MMR: Cognitive Dissonance in Action
• ECDC – Factsheet about measles
• MMWR – Measles Outbreak — Minnesota April–May 2017
• MMWR – Measles Outbreak of Unknown Source — Shelby County, Tennessee, April–May 2016
• MMWR – Measles Outbreak — California, December 2014–February 2015
• MMWR – Notes from the Field: Measles — California, January 1–April 18, 2014
• MMWR – Measles Outbreak in an Unvaccinated Family and a Possibly Associated International Traveler — Orange County, Florida, December 2012–January 2013
• MMWR – Notes from the Field: Measles Outbreak Among Members of a Religious Community — Brooklyn, New York, March–June 2013
• MMWR – Notes from the Field: Measles Outbreak Associated with a Traveler Returning from India — North Carolina, April–May 2013
• MMWR – Measles — United States, 2011
• MMWR – Measles Imported by Returning U.S. Travelers Aged 6–23 Months, 2001–2011
• MMWR – Update: Measles — United States, January–July 2008
• MMWR – Outbreak of Measles — San Diego, California, January-February 2008
• Study – Genetic Characterization of Measles Vaccine Strains
• Report – Global Distribution of Measles Genotypes and Measles Molecular Epidemiology
• Measles Surveillance Data
• Study – Identification of different lineages of measles virus strains circulating in Uttar Pradesh, North India
• Review – Elimination of endemic measles, rubella, and congenital rubella syndrome from the Western hemisphere: the US experience.
• Study – Differentiating the wild from the attenuated during a measles outbreak
• Study – Rapid Identification of Measles Virus Vaccine Genotype by Real-Time PCR
• Vaccine‐associated measles in an immunocompetent child

Last Updated on January 27, 2019