Explained: Yellow fever vaccine; necessity and riskhttps://indianexpress.com/article/explained/yellow-fever-vaccine-necessity-and-risk-5549139/

Explained: Yellow fever vaccine; necessity and risk

Yellow fever spreads through mosquitoes. It leads to death in a significant proportion of patients, which is why the vaccine is often compulsory before travelling to any of the yellow fever-endemic countries.

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Residents of the Kisenso district of Kinshasa, line up to receive yellow fever vaccines. (File/AP Photo/Jerome Delay)

The death of Prof Martin Gore, 67, former medical director of the Royal Marsden Hospital in the UK and a renowned cancer specialist, on January 10 has shocked the medical fraternity because it came after a routine yellow fever vaccination. It re-ignited a controversy over vaccines around the world.

What is controversial about vaccines, and the yellow fever vaccine in particular? Why is a yellow fever vaccine necessary?

Yellow fever spreads through mosquitoes. It is often associated with jaundice, hence the name yellow. It leads to death in a significant proportion of patients, which is why the vaccine is often compulsory before travelling to any of the yellow fever-endemic countries in parts of Africa, and Central and South America.

How safe is the vaccine?

Known as 17D, the vaccine is generally considered safe. The World Health Organization (WHO) says: “Yellow fever is prevented by an extremely effective vaccine, which is safe and affordable. A single dose… is sufficient to confer sustained immunity and life-long protection against yellow fever disease.”

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There are, however, reports in medical literature about multisystem organ failure following vaccination. In 2001, doctors from Glan Clwyd District General Hospital reported such a case in The Lancet. There are many other reports available of individual patients who died of complications after yellow fever vaccination, or of even yellow fever after vaccination.

What are the risks?

The Centers for Disease Control & Prevention (CDC), Atlanta says that while the risk of the vaccine causing serious harm or death is “extremely low”, there are complications that may arise. Among mild problems associated with the vaccine are fever with aches, soreness, redness or swelling where the shot was given.These occur in up to 1 person out of 4. They usually begin soon after the shot, and can last up to a week, CDC says. A severe allergic reaction can occur in 1 person in 55,000. A severe nervous system reaction in 1 in 125,000 and a life-threatening illness with organ failure can happen in 1 person in 250,000. More than half in the last group die.

With such risks, why go for vaccination?

There is evidence available in public health that vaccines provide return for investment — the resources spent on vaccines are more than recovered in the resources saved by the mortality and morbidity that is prevented throughout the lifetime of an individual. Nevertheless, vaccine hesitancy is on the rise.

Many vaccines introduce a pathogen inside the body. For example, the yellow fever vaccine is a live, weakened yellow fever virus. Because it is live, the body responds to it the same way as in a full-blown infection. This ensures that the body knows the vulnerabilities of that virus for the rest of the person’s life. Thus, whenever an invasion happens, blood cells that retain the memory of that virus immediately work towards defeating the nascent invasion much before it can go on to become a full-blown infection.

Is there resistance to vaccines in India?

Yes, it surfaces periodically. Last week, Delhi High Court underlined the importance of parental consent in vaccines given to children in school. Although the diphtheria vaccine is among the oldest in the Universal Immunisation Programme (UIP), the disease caused the death of 24 children in Delhi in September 2018, and 27 in Nuh district (Haryana) in December. The Health Ministry has commissioned a study on vaccine hesitancy, to be conducted by its Immunisation Technical Support Unit in association with GAVI, an international organisation supported by the Bill and Melinda Gates Foundation.

Vaccine hesitancy is a growing problem the world over. In the US, states like Minnesota have seen rising vaccine hesitancy, especially among immigrant populations, after a visit by Andrew Wakefield, a British doctor who was stripped of his licence to practice and became one of the leading voices against vaccines.