Sri Lanka: Island of hope in the midst of global measles resurgence

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Measles is considered as eliminated if local transmission is interrupted for three years.

Even as Europe is seeing a resurgence of measles with 1,60,000 cases and more than 100 deaths between January 2018 and May 2019, on July 9, Sri Lanka became the fourth country in the Asian region to eliminate it. There are many lessons that Europe and the Americas can learn from Sri Lanka.

On July 9, Sri Lanka became the fourth country in the Asian region — after Bhutan, The Maldives and Timor-Leste — to eliminate measles. Amidst an increase in the number of cases worldwide, especially in Europe, this came as an encouraging development. Measles is considered as eliminated when a country interrupts transmission of an indigenous virus for three years.

However, the viral infection has, since the beginning of 2018, seen a resurgence in 49 of the 53 countries in the World Health Organization (WHO)’s European Region. A total of 1,60,000 cases and more than 100 deaths were reported from these 49 countries between January 1, 2018 and May 30 this year. In 2018, there were nearly 82,600 cases of measles reported from 47 countries, with just 10 countries — Ukraine (53,218 cases), Serbia, Israel, France Italy, Russian Federation Georgia , Greece, Albania, Romania — accounting for 92% (nearly 75,850) of the cases.

The number of measles cases reported last year was the highest in this decade and thrice the number reported in 2017 (23,927 cases) and 15 times the cases reported in 2016 (5,273 cases). With nearly 78,000 cases reported in the first five months of this year, indications are that the number of measles cases in the European region will surpass last year’s.

Ironically, the sharp increase in measles cases in the European region comes despite vaccination coverage for the second dose being 91% in 2018. With 90% coverage in 2017, 2018 was the second consecutive year when the second dose of measles vaccination coverage had been at a record high and a vast improvement since 2000.

So despite the high coverage, what caused the spike? According to the WHO, vaccination coverage has “not been uniform across the region nor high enough to ensure herd immunity” to break the transmission cycle. Though the coverage is high at the national level, there are pockets of low coverage that is causing an “accumulation of susceptible individuals” that goes largely unnoticed till such time an outbreak occurs.

The number of cases is far less in North and South America. Of the 1,722 cases reported till June 19 this year, the U.S. alone has 1,044.

Preliminary global measles surveillance data suggests 300% increase in the number of cases in the first three months of 2019 compared with 2018. Outbreak of measles has been reported from 11 countries, including three Asian countries of Myanmar, Philippines and Thailand.

So how did Sri Lanka manage to accomplish this at this juncture even though, worldwide, there has been a 300% increase in the number of cases in the first three months of this year, compared to 2018? The answer lies in an increased, and a wider, vaccination coverage for both doses.

While global coverage for the first dose of vaccine has remained stagnant at 85% and for the second dose, it is still at 67%, the coverage for Sri Lanka has been above 95% for both the first and second doses. The vaccine is provided to children under the routine national immunisation programme.

The island nation, where measles is a notifiable infection, has also carried out periodical mass vaccination campaigns to reach the small pockets of unimmunised children. Sri Lanka also has strong surveillance in place.

Sri Lanka had encountered a few bumps in its path to eliminating measles. In 1984, Sri Lanka introduced measles vaccine in the national immunisation programme and set the goal of eliminating measles. Though severe local outbreaks were reported, the annual incidence declined till 1999.

During Sri Lanka’s measles epidemic of 1999-2000, nearly 15,000 cases were reported following which a two-dose vaccine schedule was introduced, resulting in a sharp decline in incidence. The country reached an elimination target of less than five per one million people in 2011.

But in 2012, the measles immunisation schedule was changed following which babies no longer received measles vaccine at the age of nine months but a measles, mumps and rubella (MMR) vaccine on completing 12 months. Following this, in 2013, the country witnessed its last major measles epidemic. Besides other reasons, the change in immunisation schedule was seen as a possible cause.

The MMR vaccine schedule was again changed following a sero-survey data. Babies now began receiving the first dose at nine months and second dose at the age of three years. The country reported its last case of measles caused by an indigenous virus in May 2016.

Published in The Hindu on July 25, 2019

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