With better sanitation and hygiene, hepatitis A infection in Kerala has been witnessing an epidemiological transition — the infection is shifting from early childhood to adolescents and young adults. The infection is mild in children younger than six years and in almost 70% of the cases, hepatitis A infection is asymptomatic in this age group. However, in older children, the infection is very often symptomatic and in rare cases can cause liver injury and even death.

Kerala has recorded hepatitis A outbreaks with great regularity in the past two decades. There has been at least one outbreak with many deaths each year since 2017, including 2024. This year, a large number of hepatitis A cases have been reported from four districts of Kozhikode, Malappuram, Thrissur and Ernakulam. As of May 30, over 2,400 confirmed cases and 18 confirmed deaths have been reported, making the 2024 outbreak the biggest in terms of number of cases.

Since a single infection of hepatitis A leads to lifelong immunity, children infected when young are immune to hepatitis A virus as adults. However, due to better sanitation and hygiene, very often children in Kerala do not get infected with hepatitis A thus making them vulnerable to severe infections and even serious health problems when infected as adults. Vaccination is one way to reduce outbreaks and help reduce out-of-pocket expenditure. As per studies done in Kerala earlier, the average out-of-pocket expenditure when an adult is infected is nearly ₹25,000.

A paper published recently in the journal PLOS ONE has found that hepatitis A vaccination of children in Kerala aged one year and adolescents aged 15 years using either a live, attenuated vaccine or an inactivated vaccine is cost-effective. While one dose is sufficient in the case of a live, attenuated hepatitis A vaccine, the inactivated vaccine requires two doses for full immunisation. Besides other factors, the cost-effective analysis took into account the cost of the vaccine, the number of doses needed for full immunisation, coverage needed, and the total number of individuals to be vaccinated in the two age groups — 460,000 children aged one year and 502,600 adolescents aged 15 years.

“Our cost-effectiveness evidence supports the inclusion of hepatitis A vaccination into the vaccination programme for children aged one year and individuals aged 15 years in Kerala,” says the paper.

“Rs.9,330 million and ₹4,649 million would be required for vaccinating 15-year-old individuals using inactivated and live attenuated vaccination, respectively. In the case of children aged one year, ₹7,730 million and Rs. 3,394 million would be required for vaccinating them using inactivated and live attenuated vaccination, respectively. The inactivated vaccine will cost more than live attenuated for both children aged one year and adolescents aged 15 years [as two doses are needed in the case of inactivated vaccine],” Dr. Montarat Thavorncharoensap from the Mahidol University Health Technology Assessment Graduate Program, Mahidol University, Bangkok, Thailand and the corresponding author says in an email to The Hindu.

Researchers from two ICMR institutions — the Chennai-based National Institute of Epidemiology (NIE) and the Pune-based National Institute of Virology (NIV) — were involved in the study and are coauthors of the paper.

Compared with ₹15,202 million spent for treatment at the end of five years when vaccination is not introduced for adolescents aged 15 years, the study found that at the end of five years, Kerala will end up saving ₹5,872 million when an inactivated vaccine is used and ₹10,553 million if a live, attenuated vaccine is used.

In the case of children aged one year, the study found that ₹1,402 million will be spent on treatment at the end of five years when vaccination is not introduced. At the end of five years, the total cost of vaccinating with a live, attenuated vaccine will be ₹1,992 million, while it will be ₹6,328 million when an inactivated vaccine is used.

While at the end of five years, the State will end up saving millions when either of the vaccines is used in the case of adolescents, in the case of children aged one year, the expenses towards treatment do not exceed the cost of vaccination. So at the end of five years, vaccination does not lead to net savings in the case of children aged one year. “We have calculated it only for five years. But since hepatitis A vaccination will continue to protect children beyond five years, the State will eventually end up saving millions each year in the case of children aged one year,” says the first author Dr. Yogesh Krishnarao Gurav from the Health Technology Assessment Group at NIV Pune.

The higher cost savings in the case of adolescents even at the end of five years compared with one-year-old children is because adolescents, like adults, are more prone to infection, while in early childhood the infection is not severe, says Dr. Thavorncharoensap.

While one dose of the live, attenuated vaccine is sufficient to provide full protection, two doses are needed in the case of the inactivated vaccine.

“The cost of an inactivated vaccine, which requires two doses, is almost double that of the live, attenuated vaccine. Therefore, live attenuated seemed to have a better cost-effectiveness profile. However, it should be noted that both vaccines are cost-saving, which means that the cost of vaccines is less than the benefits,” she says.

For the cost-effective analysis, the vaccine coverage rate of 90% has been taken into account based on the fact that the DTP-Hib-Hepatitis B vaccination coverage in Kerala under the universal immunisation programme is over 90%. But the vaccine coverage rate in Kerala is only for infants and little children and does not include adolescents aged 15 years. Since high coverage is necessary for benefits to be seen, can it be achieved in the case of adolescents who are outside the universal immunisation programme? “To achieve high coverage in adolescents is quite a challenge. Unlike for children in which the vaccine can be incorporated into the immunisation programme, school-based together with effective campaigns might be a good strategy for adolescents,” Dr. Thavorncharoensap says.