by Dr Milton Lum
Diarrhoea is common among infants and young children. Rotaviruses are a leading cause of severe and dehydrating diarrhoea. The rotavirus is a RNA virus of the reoviridae family.
It comprises proteins that stimulate the production of antibodies by the infected person, with five serotypes responsible for 90% of human rotavirus infections. Rotaviruses affect the majority of children worldwide before the age of 3 years, and in most developing countries, before the age of 1 year.
An infected child sheds large amounts of the rotavirus in the stools and vomit for many days. The virus is spread mainly by the faecal-oral route, directly from person to person or indirectly from contaminated fomites. It affects the mucosal lining of the small intestine. The destruction of the affected cells reduces the digestion and absorption of food ingested, resulting in a secretory diarrhoea with the loss of fluids and electrolytes into the intestine.
The spectrum of rotavirus infection varies from a transient mild diarrhoea to severe gastroenteritis with dehydration, electrolyte imbalance, shock and death. The World Health Organization (WHO) estimates that the rotavirus causes more than 500,000 fatalities annually, mostly in developing countries.
The initial rotavirus infection in infants aged more than 3 months often leads to severe gastroenteritis. Subsequent re-infections are usually without symptoms (asymptomatic) or there is mild gastroenteritis.
The onset of rotavirus infection is abrupt with fever and vomiting, followed by watery diarrhoea. The symptoms usually improve within 3 to 7 days but may last 2 to 3 weeks. If no complications result, recovery is usually complete.
Treatment is supportive. The dehydration and electrolyte imbalance has to be corrected. There is no specific antiviral therapy available.
The disease burden of rotavirus infection in Malaysia is not known as it is not a notifiable infection. However, Mat Ludin and his colleagues analysed data from stool samples of children with diarrhoea and acute gastroenteritis who were admitted to Hospital Universiti Sains Malaysia in Kubang Kerian.
Out of 1,097 stool samples tested between 1991 and 2000, 207 samples or 18.8% were positive for rotavirus. The infection occurred most frequently in infants and young children aged 6 months to 2 years. The highest infection was recorded in 2000 (48 cases or 34.1%) and the lowest in 1999 (5 cases or 6.6%).
The rotavirus vaccines are live attenuated vaccines, that is, live disease producing viruses modified in the laboratory so that it stimulates the production of antibodies.
Two vaccines are available : a monovalent human rotavirus vaccine and a pentavalent bovine-human, reassortant vaccine.
Both vaccines have demonstrated their safety and efficacy in trials carried out in western developed countries and South America. The vaccines are now being used in many developed and developing countries.
The interchangeability of both vaccines has not been worked out, so there should be no switching from one type of vaccine to another in subsequent doses. Both types of rotavirus vaccines are given orally. The monovalent human rotavirus vaccine is given in a two-dose regime. The first dose is given to infants at six to 12 weeks of age, followed by the second dose at least four weeks later. The schedule should be completed by the age of 16 weeks and not later than 24 weeks.
The pentavalent bovine-human reassortant vaccine is given in a three-dose regime. The first dose is given to infants at 6 to 12 weeks of age followed by two subsequent doses at intervals of 4 to 10 weeks. All the doses should be completed by the age of 32 weeks.
It is recommended that the initial dose of both types of vaccines should not be given to infants at more than 12 weeks of age, as the safety of the vaccines after the age of 12 weeks has not been established. The vaccines can be given at the same time as other vaccines, including oral polio vaccine, as it does not interfere with the body’s response to other vaccines.
Effectiveness and Safety
Both rotavirus vaccines are considered to be of equal effectiveness and safety. They provide 90% to 100% protection against severe rotavirus infections and about 75% to 85% protection against rotavirus infection of any severity. The degree of protection is influenced by the immunisation schedule of the vaccine and the population studied.
The duration of protection of rotavirus vaccines is yet to be worked out. However, it has been demonstrated that the protection against severe rotavirus infection extends into the child’s second year of life for both vaccines. Studies have shown that both vaccines are safe. The Global Advisory Committee on Vaccine Safety stated that there was no indication of any increased risk of intussusceptions or other adverse events associated with both vaccines.
Rotavirus vaccines are well tolerated and reactions are minimal.
On rare occasions, there may be mild and transient gastrointestinal or respiratory symptoms associated with the vaccines. This is usually self-limiting.
Vaccination is not advised in those who are potentially immunocompromized, that is, HIV positive; have hypersensitivity reactions to the vaccine; or have a history of intussusceptions or intestinal conditions that predispose to intussusceptions. It is advisable to postpone vaccination in those who have high fever or ongoing gastroenteritis.
In conclusion, there is no published data on the prevalence of rotavirus infection in the country although the infection is diagnosed often enough for such studies to be carried out. Data on the true burden of the infection locally is needed before formulation of a public policy on the vaccine.
One should always be mindful that rotavirus vaccines provide protection against gastrointestinal rotavirus infections only and not other gastrointestinal infections.
More info on DIARRHOEA HERE.