measles vaccine history Archives

Pennsylvania crossed a thousand measles cases this week. The state is at 1,078 across 41 counties, with 207 hospitalizations and five measles-associated deaths, and Lancaster County alone accounts for 401 of them. Nationally we are at roughly 3,880 cases. That is the highest annual total since 1991.

New York’s governor declared a disaster emergency on Monday so that paramedics, pharmacists and midwives can give vaccines. Florida’s health department met in Orlando this week to consider ending its school and daycare vaccination requirement altogether.

Almost all of the coverage is about children, because that is where the cases are.

I have had one of these myself, by video. An unvaccinated child, high fever, body aches, and a rash whose appearance made me think measles before I thought of anything else. Looking like measles is not the same as being measles. Confirmation takes a swab for PCR and a blood sample for measles IgM, and neither of those travels down a camera, so that visit ended where it had to end, in a referral for testing in person.

That is the honest limit of the work I do. I could recognize it. I could not prove it.

The question I get by video is a different one, and it comes from adults. Some version of: am I still covered?

It is a better question than it sounds, because for a specific group of people the honest answer is no.

The 1963 to 1967 problem

There were two measles vaccines licensed in 1963. One was a live attenuated vaccine, which is the ancestor of the MMR we give now. The other was an inactivated vaccine, a killed-virus product that was pulled from the market in 1967 because it did not work well enough.

It did something worse than not working. Some people who got the killed vaccine and later met the real virus developed atypical measles syndrome, an unusually severe illness with high fever, an odd rash that starts on the extremities, and pneumonia.

So the guidance is specific. Anyone vaccinated before 1968 with killed measles vaccine, or with a vaccine of unknown type, should be revaccinated with at least one dose of live attenuated measles vaccine. If you are in a high-risk group, that becomes two doses.

The number of people affected is small. The CDC puts it at under five percent of adults. Immunize.org estimates fewer than a million Americans.

Here is the practical problem with a small number. Almost nobody born in that window knows which shot they got. The record, if it exists at all, is a line in a pediatrician’s file from sixty years ago, and that pediatrician has been retired for thirty of them. “Measles vaccine, 1965” does not tell you which product it was.

Which is why the rule says unknown type counts the same as known killed. If you cannot establish it was the live vaccine, you are treated as though it was not.

If you were born before 1957

You are presumed immune and you do not need anything.

That cutoff is not a guess about vaccines. It is a statement about how common measles was. Before the vaccine existed, essentially everyone caught it in childhood, so the assumption is that you already did, whether or not you remember it.

One exception, and it is the one that applies to me and to anyone else reading this who works in health care. For healthcare personnel, facilities should consider vaccinating staff born before 1957 who have no laboratory evidence of immunity and no laboratory confirmation of past disease. The presumption is good enough for the general public. It is not good enough for someone standing in a room with a febrile child.

Should you get a titer drawn?

Usually not, and this is where I disagree with how the question is often handled.

The CDC does not recommend routinely screening adults for measles immunity outside an outbreak area, and it does not recommend testing after vaccination to confirm it took. If you have documentation of two MMR doses, you are done. No blood draw adds anything.

A titer is useful in one specific situation, which is when you genuinely do not know your history and the result would change what happens next. Positive measles IgG means immune. Negative or equivocal means treat as non-immune, unless you meet one of the other criteria such as birth before 1957.

But consider the arithmetic before you order it. An MMR dose costs less than the antibody test in most places, takes one visit instead of two, and carries no penalty if you turn out to have been immune all along. An extra dose in someone who is already protected does nothing at all. It does not boost, it does not harm, it simply has no target.

So for most adults who are uncertain, getting the shot is faster and cheaper than proving you do not need it.

The exception worth naming is pregnancy. MMR is a live vaccine and is not given during pregnancy, so a woman who is pregnant and uncertain about her status gets the titer instead, and the vaccine afterward if she needs it.

About the death count, since you will see it argued about

Pennsylvania reports five measles-associated deaths this year. The CDC’s national count is two, and the CDC’s database does not say which states those two are in.

That gap is real and it is worth understanding, because it is being read as evidence of a cover-up in one direction and of inflated numbers in the other.

The mechanism is duller than either. The CDC moved to counting measles deaths from National Center for Health Statistics mortality data, which is built from death certificates and lists an underlying cause, rather than from state health department reports. NCHS data is designed to measure long-term trends across a population. It was not built to adjudicate individual infectious disease cases in the middle of an outbreak, and it runs on a slower clock, which is the substance of what the outside experts objecting to the change have said.

Pennsylvania uses a different definition: a laboratory-confirmed measles infection and death within thirty days of symptom onset, absent an obvious unrelated cause such as a car crash.

Both definitions are defensible. They will produce different numbers during a fast-moving outbreak, and the federal one will lag.

There is also a political layer, which I will describe rather than referee. The CDC initially included Pennsylvania’s first two deaths and then removed them pending review, after the Health Secretary publicly questioned whether measles had caused them. That detail was first reported by a Substack citing an anonymous CDC employee, so I hold it more loosely than the rest of this. The count later returned to two after NCHS verified one death. Pennsylvania has since conditioned its request for federal Epi-Aid assistance on the CDC publicly recognizing the state’s full count.

What I would say clinically is narrow. Of Pennsylvania’s five, two were unvaccinated adults, aged 18 and 40, and two were infants too young to be vaccinated. That pattern is what measles mortality has always looked like. It kills the unprotected and the too-young-to-protect, and it does so through pneumonia and encephalitis rather than through the rash anyone remembers.

As the infectious disease physician Amesh Adalja put it, to the public a gap like this looks like either incompetence or concealment. Neither is true here, and the fact that neither is true is not doing much to help.

What I would actually do

If you have records showing two MMR doses, nothing. You are protected and the protection does not fade.

If you were born before 1957 and do not work in health care, nothing.

If you were vaccinated between 1963 and 1967, or you have no idea what you got and you were born after 1957, get one dose of MMR. Do not spend three weeks trying to find a sixty-year-old paper record first.

If you are pregnant and uncertain, ask for the titer, and plan the vaccine for after delivery.

And if you have an infant under twelve months in a household traveling to an outbreak area, that is a real conversation with your pediatrician about an early dose, which is a thing that exists and is not widely known.

The Bottom Line

Measles is at a thirty-five year high, and the people getting sick are overwhelmingly children who were never vaccinated. That is a different problem from the one most adults are asking me about.

For adults, the short version is that the vaccine works, it does not wear off, and the only real gap is a four-year window in the sixties when a product that did not work well was in use. If you fall in that window or you simply cannot establish what you got, a single MMR dose closes it, and it is cheaper and faster than proving you were fine all along.

Sources

Pennsylvania Department of Health Provides Statewide Update on Measles Outbreak as Cases Reach 1,078 in 41 Counties. Pennsylvania Department of Health, October 7, 2026. https://www.pa.gov/agencies/health/newsroom/pa-department-of-health-provides-statewide-update-on-measles-out9
Measles cases surpass 1,000 in Pennsylvania amid the state’s largest outbreak in decades. ABC News, October 2026. https://abcnews.com/Health/measles-cases-surpass-1000-pennsylvania-outbreak-continues-spread/story?id=137002024
Pennsylvania confirms fifth measles-associated death as US outbreak grows. Al Jazeera, September 30, 2026. https://www.aljazeera.com/news/2026/9/30/pennsylvania-confirms-fifth-measles-associated-death-as-us-outbreak-grows
New York governor declares measles emergency. CT Mirror, October 7, 2026. https://ctmirror.org/2026/10/07/new-york-measles-emergency-hochul
Vaccine change may bring largest measles outbreak ever. WGCU, October 7, 2026. https://wgcu.org/health/2026-10-07/vaccine-change-may-bring-largest-measles-outbreak-ever
Measles Cases and Outbreaks. Centers for Disease Control and Prevention. https://www.cdc.gov/measles/data-research/index.html
Measles Vaccine Recommendations. Centers for Disease Control and Prevention. https://www.cdc.gov/measles/hcp/vaccine-considerations/index.html
Questions About Measles. Centers for Disease Control and Prevention. https://www.cdc.gov/measles/about/questions.html
Ask the Experts: MMR (Measles, Mumps, and Rubella). Immunize.org. https://www.immunize.org/ask-experts/topic/mmr/
Measles Prevention: Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR. https://www.cdc.gov/mmwr/preview/mmwrhtml/00041753.htm
CDC’s new tracking method for measles deaths puzzles experts. CIDRAP, University of Minnesota. https://www.cidrap.umn.edu/measles/cdc-s-new-tracking-method-measles-deaths-puzzles-experts
Measles is spreading across the US and officials can’t agree on the death toll. The Conversation, 2026. https://theconversation.com/measles-is-spreading-across-the-us-and-officials-cant-agree-on-the-death-toll-293234
Changes to CDC Vaccine Recommendations in 2025 and 2026. Congressional Research Service, IN12684. https://www.congress.gov/crs-product/IN12684

Dr. Scott Rennie

Tag: measles vaccine history

Are You Still Protected From Measles? The 1963 to 1967 Vaccine Gap and What Adults Should Do