Tag: measles vaccination

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How Canada Lost its Measles Elimination Status Highlights Threat of Immunity Gaps

On By ModernMedia

90% of cases occurred in historically under-vaccinated communities
Findings offer insights for countries aiming to retain or regain their elimination status 

Photo by Gustavo Fring on Pexels

The outbreak that contributed to Canada losing its measles elimination status in November 2025 was concentrated in historically under-vaccinated communities with close social networks across Canada, the US, Mexico, and beyond, creating opportunities for cross-border transmission, concludes a study published by The BMJ.

The researchers say the findings highlight the ongoing risk of measles resurgence in countries that have previously successfully controlled the disease, and underscore the importance of culturally tailored community engagement to build trust and confidence in vaccination and prevent future outbreaks.

Canada achieved measles-free status in 1998 after introducing a two-dose vaccine schedule and a national catch-up programme for school-aged children, but lost it in November 2025 after a measles outbreak that involved several provinces. In Ontario, the outbreak disproportionately affected historically under-vaccinated communities – groups with historically low vaccine coverage and close social networks across Canada, the US, and Mexico.

To better understand the course of this outbreak and its impact, researchers analysed measles cases reported to Ontario’s public health surveillance system during the outbreak period (28 October 2024 to 6 October 2025).

The outbreak consisted of 2377 cases (2064 confirmed and 313 probable) over 49 weeks. Most cases (90%) occurred among members of historically under‑vaccinated communities, with limited spillover into the broader population.

Among the 2377 cases, around three quarters (73%) occurred in individuals aged 19 years or younger, 2,121 (89%) were unvaccinated and 97 (4%) had unknown vaccination status.

The outbreak was associated with 166 admissions to hospital, 13 admissions to an intensive care unit, 51 infections during pregnancy, 10 congenital measles infections, one case of encephalitis (brain inflammation), and one infant death.

Laboratory tests identified a distinct measles virus strain that was subsequently detected elsewhere in Canada, and in the US, Mexico, and the Netherlands due to close social ties within and between under-vaccinated communities combined with the high transmissibility of measles.

The researchers acknowledge that their analysis is subject to limitations inherent to public health surveillance data, and note that the number of cases and associated complications may be higher than what is reported in the study.

In addition, the proportion of cases in under-vaccinated communities is likely to be conservative, reflecting challenges in data collection for a variety of reasons, including mistrust among some community members and concerns from public health staff about the risk of stigmatisation of affected groups during the outbreak.

However, they say this measles outbreak illustrates the fragility of measles elimination in the presence of substantial immunity gaps within domestically and globally interconnected communities.

Limited spillover beyond these communities also highlights a high degree of vaccine acceptance in the population at large and the success of local partners in closing immunity gaps as part of the outbreak response, they add.

“Strengthening of immunisation systems, improving vaccine coverage, and sustaining culturally appropriate engagement to continue to build trust in immunisation will be essential to prevent future vaccine preventable disease outbreaks and to support re-establishing measles elimination,” they conclude.

In a linked editorial, Jennifer Nuzzo at Brown University School of Public Health warns that Canada’s loss of elimination status signals growing vulnerability to infectious disease threats, even in well-resourced high-income countries.

She argues that elimination requires not just high vaccination coverage, but also sensitive disease surveillance, laboratory capacity, rapid outbreak investigations, timely reporting, effective public health responses, and public trust.

Failing to stop measles within national borders also makes it harder for countries around the world to keep the disease at bay, she adds.

She urges countries to recommit to measles elimination “not simply to restore a designation, but to stop a dangerous, preventable disease and strengthen the public health systems that protect their own populations and those of their neighbours from other serious infectious threats.”

Source: The BMJ Group

Categories : Obstetrics & Gynaecology VaccinesTags :

Birth by C-section More than Doubles Odds of Measles Vaccine Failure

On By ModernMedia
Photo by Christian Bowen on Unsplash

A study by the University of Cambridge, UK, and Fudan University, China, has found that a single dose of the measles jab is up to 2.6 times more likely to be completely ineffective in children born by C-section, compared to those born naturally.

Failure of the vaccine means that the child’s immune system does not produce antibodies to fight against measles infection, so they remain susceptible to the disease.

A second measles jab was found to induce a robust immunity against measles in C-section children.

Measles is a highly infectious disease, and even low vaccine failure rates can significantly increase the risk of an outbreak.

A potential reason for this effect is linked to the development of the infant’s gut microbiome — the vast collection of microbes that naturally live inside the gut. Other studies have shown that vaginal birth transfers a greater variety of microbes from mother to baby, which can boost the immune system.

“We’ve discovered that the way we’re born – either by C-section or natural birth – has long-term consequences on our immunity to diseases as we grow up,” said Professor Henrik Salje in the University of Cambridge?’s Department of Genetics, joint senior author of the report.

He added: “We know that a lot of children don’t end up having their second measles jab, which is dangerous for them as individuals and for the wider population.

“Infants born by C-section are the ones we really want to be following up to make sure they get their second measles jab, because their first jab is much more likely to fail.”

The results are published today in the journal Nature Microbiology.

At least 95% of the population needs to be fully vaccinated to keep measles under control but the UK is well below this, despite the Measles, Mumps and Rubella (MMR) vaccine being available through the NHS Routine Childhood Immunisation Programme.

An increasing number of women around the world are choosing to give birth by caesarean section: in the UK a third of all births are by C-section, in Brazil and Turkey over half of all children are born this way.

“With a C-section birth, children aren’t exposed to the mother’s microbiome in the same way as with a vaginal birth. We think this means they take longer to catch up in developing their gut microbiome, and with it, the ability of the immune system to be primed by vaccines against diseases including measles,” said Salje.

To get their results, the researchers used data from previous studies of over 1500 children in Hunan, China, which included blood samples taken every few weeks from birth to the age of 12. This allowed them to see how levels of measles antibodies in the blood change over the first few years of life, including following vaccination.

They found that 12% of children born via caesarean section had no immune response to their first measles vaccination, as compared to 5% of children born by vaginal delivery. This means that many of the children born by C-section did still mount an immune response following their first vaccination.

Two doses of the measles jab are needed for the body to mount a long-lasting immune response and protect against measles. According to the World Health Organization, in 2022 only 83% of the world’s children had received one dose of measles vaccine by their first birthday – the lowest since 2008.

Salje said: “Vaccine hesitancy is really problematic, and measles is top of the list of diseases we’re worried about because it’s so infectious.”

Measles is one of the world’s most contagious diseases, spread by coughs and sneezes. It starts with cold-like symptoms and a rash, and can lead to serious complications including blindness, seizures, and death.

Before the measles vaccine was introduced in 1963, there were major measles epidemics every few years causing an estimated 2.6 million deaths each year.

The research was funded by the National Natural Science Foundation of China.

The original text of this story is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Licence.

Source: University of Cambridge