The UK's public health protection agency on Friday sounded a "national call to action" for more measles jabs for children because of falling vaccination rates and fears a current outbreak could spread.

Jenny Harries, head of the UK Health Security Agency (UKHSA), warned that measles was spreading among unvaccinated communities.

She acknowledged that some members of the Muslim community were wary of the vaccines because one on offer had a pork-based derivative.

But she said she wanted to let people know that an alternative was available and was "very effective".

People have "forgotten what measles is like", Harries told BBC radio, pointing out that it could even be fatal in rare cases.

The UK had previously achieved "measles elimination status", she said.Now, however, the average number of children starting school having had both doses of the combined measles, mumps and rubella (MMR) vaccine stands at only 85 percent.

Highlighting the central West Midlands region of England, she said an ongoing  outbreak there had seen 216 laboratory-confirmed cases and 103 "likely" cases  since October 1, 2023.

Of those, 80 percent were found in the city of Birmingham. Vaccination rates across the country have been dropping, but there are particular concerns about some areas, including parts of London.

The lowest rates nationally were seen in the capital, with one area -- Hackney in the east -- having vaccinated only 56.3 percent of children, according to the latest health service figures.

Asked which communities were less likely to take up vaccinations, Harries said that "for the West Midlands, for those in Muslim communities, they will be not keen to take up one of the MMR vaccines that we offer, which has a pork-based derivative".

According to the World Health Organization (WHO), about 83 percent of the world's children received one dose of measles vaccine by their first birthday -- the lowest since 2008.

In 2021, there were an estimated 128,000 measles deaths worldwide, mostly among under-vaccinated or unvaccinated children under the age of five.