How Fast Do Measles Vaccines Work?

In light of this news, many may be considering their own or their kids’ vaccination history. It’s not too late to get a measles vaccine, but it’s important to know that the full level of protection doesn’t kick in straight away.

What vaccine is recommended for measles?

The Centers for Disease Control and Prevention (CDC) recommends the MMR vaccine be used to protect against measles. It’s a combination vaccine that immunizes against three diseases: measles, mumps, and rubella. To get the maximum level of protection, the agency recommends that everyone receive two shots, ideally at around 1 year and then 4 years old. 

That said, it’s never too late to get a top-up if you didn’t get both shots as a kid, or if you’re not sure of your vaccination status. This is particularly important for students going off to college, healthcare workers, and anyone planning international travel. 

Older adults who may have missed out on the combination vaccine might also consider getting an MMR shot. The MMR was approved in the US in 1971, before which there had been a measles-only vaccine available for a few years. If you’re unsure of your measles immunity status, it’s best to speak with a healthcare provider. 

How long does it take for a measles vaccine to work?

It takes about two weeks to reach the full level of protection from a dose of MMR. 

This is comparable to other vaccines, such as the mRNA COVID-19 vaccines. Some other vaccines, such as the rabies vaccine, kick in more quickly, within days – that’s why the rabies shot is used as part of post-exposure prophylaxis when it’s suspected that someone may have been exposed to the virus.

As well as taking different lengths of time to kick in fully, different vaccines vary in the longevity of protection they provide. For example, we know that COVID-19 vaccine immunity wanes relatively quickly, so booster shots are needed.

The MMR performs well on this. One dose of the MMR should give about 93 percent protection against measles. The second dose ups this to around 97 percent, as well as ensuring that you’re protected for the long term. 

A 2024 study found that while the vaccine remains very effective, offering a good degree of lifelong immunity, that protection does start to wane slightly over time. This explains why some double-vaccinated people still do catch measles, albeit with generally milder symptoms.

The answer to this, the researchers stress, is to improve vaccine coverage overall within the population. 

“If there were no outbreaks, this small amount of waning would not show up in any data. The key issue here is coverage, not the effectiveness of the vaccine,” said lead author Dr Alexis Robert in a statement. 

How does the MMR vaccine work?

The MMR vaccine is a live attenuated vaccine, meaning it contains weakened forms of the three viruses it protects against. When the shot is administered, it provokes an immune reaction, and the body starts to produce specific antibodies and immune cells targeted at the measles, mumps, and rubella viruses. 

This process takes time, hence the full level of protection is not reached until about two weeks later. In the meantime, a small proportion of people will experience side effects. In most cases, these are not serious, and can include things like pain at the injection site, fever, and a mild rash. 

There is absolutely no link between the MMR shot and autism – rigorous scientific research has consistently failed to find any basis for this claim, despite the decades of mis- and disinformation on the subject. 

There is also no evidence of any benefit to splitting the shots up into individual doses. If anything, that only increases the time interval for which someone is not protected against these diseases. 

With measles – once eliminated in the US – on the rise again, the best time to get vaccinated for you and your child is right now. 

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.   

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.