TB transmission among the elderly in China may increase to 53 per cent by 2050 from 18 per cent in 1990 while their burden of TB disease may rise to 71 per cent from 13 per cent over the same period, according to preliminary research presented at the Fourth Global Forum on TB Vaccines in Shanghai, China (21-24 April).
Extending vaccination to older age groups may provide greater impact than among either infants or adolescents, Rebecca Harris, an epidemiologist at the London School of Hygiene and Tropical Medicine and one of the experts involved in the research, tells SciDev.Net.
China has gained international attention for successfully reducing TB transmission in the past 20 years. But the country still has approximately 980,000 new TB cases each year, second to India, and 41,000 deaths annually, according to the WHO. Additionally, a third of the world’s drug-resistant TB cases are found in China. Globally, an estimated 1.5 million people died of TB and some 480,000 people developed the multidrug resistant type.
The reason for this is China’s increasingly elderly population.
“Many of the older people who lived through those years when TB was even worse are latently infected so they can and do get the disease in their later years,” Ann Ginsberg, chief medical officer at Aeras, a nonprofit organisation specialising in vaccines, tells SciDev.Net.
In contrast, the decline in TB transmission in China in recent years has resulted in lower numbers of young people infected, which means fewer young people will develop the disease in the future.
The study also found that developing a vaccine that works in latently infected individuals may decrease the rate of TB in China by almost a third by 2050 if given to older adults. At present, the only TB vaccination available is Bacillus Calmette-Guérin (BCG), which in most countries is given to infants, never the elderly.
TB is an infectious disease of the lungs causing symptoms such as severe coughing and chest pains. While there are cures for various types of TB, such treatments in China cost over half the average annual household income for the rural poor, according to Aeras. Since each person with active TB usually infects up to 15 people, entire communities could be at risk particularly in crowded areas.
The WHO list of 22 countries with a high burden of TB which includes six countries in South-East Asia — Cambodia, Indonesia, Myanmar, Philippines, Thailand and Vietnam. South-East Asia and the Western Pacific regions accounted for the largest number of new TB cases with 56 per cent of the new cases worldwide.
This article has been produced by SciDev.Net's South-East Asia & Pacific desk.