Corynebacterium diphteriae is a bacterium which can cause myocarditis (inflammation of the heart muscle), inflammation of nerves and kidney problems. It is transmitted by contact, by contaminated objects or through the air. According to World Health Organization (WHO) data, incidence of diphtheria is on the rise: countries reported more than 7,000 cases in 2016, and almost 17,000 in 2018. Death occurs in 5% to 10% of those infected, mainly in children under 5 years of age.
Caused by Clostridium tetani bacterium, which is commonly found in soil, saliva, dust and manure, the infection is characterised by muscle spasms. The tetanus toxoid vaccine protects effectively against all forms of tetanus and has reduced incidence rates globally. Neonatal tetanus continues to be a major killer of newborns and can be prevented by providing the vaccine to women of childbearing age, either before or during pregnancy. According to WHO, there were a total of 15,103 cases of tetanus in 2018.
PERTUSSIS (WHOOPING COUGH)
Pertussis or whooping cough is a highly infectious airborne bacterial disease. It spreads easily from infected persons and is fatal in 1 in 200 cases among infants. The pertussis vaccine is effective at preventing illness, but its protection may wane after three to six years.
HAEMOPHILUS INFLUENZAE TYPE B
Haemophilus influenzae type b (Hib) is a deadly bacterium which can cause meningitis, pneumonia and septicaemia. Hib is the third-leading vaccine-preventable cause of death in under-fives. In developing countries, where the vast majority of Hib deaths occur, the disease leaves up to 35% of survivors with disabilities. By 1999, 10 years after being licensed, Hib vaccine was only available in one low-income country.
Spread through sneezing and coughing, Hib in the pre-vaccine era was the leading cause of childhood meningitis – inflammation of the membranes covering the brain and spinal cord. Many survivors suffer paralysis, deafness, mental retardation and learning disabilities.
Even today, almost 30 years after safe and effective Hib conjugate vaccines were first licensed, Hib remains a significant cause of pneumonia and meningitis, mainly in children. Globally, the disease accounts for approximately 200,000 child deaths every year, most of them in low-income countries. Hib can be treated with antibiotics, but lack of access to adequate medical facilities and increasing levels of antibiotic resistance lead to high mortality rates.
After Canada became the first country to introduce Hib vaccine in 1986, uptake was fast; by 1998, 50% of high-income countries had introduced the vaccine into their immunisation programmes – leading to dramatic declines in the incidence of Hib disease. However, high costs meant low-income countries could not afford the vaccine. The Gambia was the lone exception, becoming the only developing country to introduce Hib vaccine thanks to a manufacturer's donation in 1997. In 2006, WHO issued a powerful recommendation for Hib vaccines, urging that it be included in all routine immunisation programmes around the world.
HepB can cause liver cancer – one of the most lethal types of cancer
The hepatitis B (hepB) virus is the leading cause of liver cancer and is 50 times more infectious than HIV. While infections occur mostly in young children, the deadly consequences of the virus usually strike later in life in the form of liver disease, including cirrhosis and liver cancer. In 2015, an estimated 257 million people worldwide were chronically infected with the hepB virus, which claimed approximately 887,000 lives due to acute or chronic liver disease.
Transmission of the virus from mother to newborn infant is a major contribution to disease in regions such as Asia and the Pacific Rim, where infection is widespread. The majority of cases could be avoided through vaccination. The vaccine is 98% effective in preventing infection and the development of chronic disease and liver cancer due to hepB.
HepB vaccines became available in 1982, with Italy becoming the first high-income country to introduce the vaccine into its national immunisation programme only a year later. Yet it was only in 1994 that Zimbabwe became the first low-income country to follow WHO's 1992 recommendation that childhood hepB vaccination be included in all immunisation programmes.
By the late 1990s, the hepB vaccine had been on the market for two decades but was taking longer than the average 15 years usually required for a new vaccine to reach large numbers of the world's poorest children. And by 2000, the infection was claiming an estimated 900,000 lives each year – most of them in low-income countries. Yet only 22 low-income countries had access to the hepB-containing vaccine.