Hospitalizations for respiratory syncytial virus pneumonia may be substantial in low-income settings

There were more than 1,000 hospitalizations for respiratory syncytial virus per 100,000 infants in a region of rural Kenya, according to findings of a recent study.

Prospective surveillance of severe and very severe pneumonia was conducted in the Kilifi district hospital in coastal Kenya between 2002 and 2007. Eligible participants were children aged younger than 5 years. The researchers screened nasal specimens for respiratory syncytial virus antigen and estimated incidence rates for the well-defined population.

There were 7,359 patients with severe or very severe pneumonia among 25,149 hospital admissions (29%). There were 6,026 (82%) patients enrolled.

Respiratory syncytial virus prevalence rates were 27% (32% among infants) during epidemics and 15% (20% among infants) overall. Among infants aged 3 months or older, the proportion of case patients was 65%. That proportion was 43% among infants aged 6 months or older.

The average number of hospitalizations per 100,000 children aged younger than 5 years was 293 (95% CI, 271-371 hospitalizations per 100,000 children aged younger than 5 years). Among infants, the rate was 1,107 hospitalizations per 100,000 (95% CI, 1,102-1,211 hospitalizations per 100,000 infants).

Hospital admission rates doubled in the region closest to the hospital, according to the results.

The mortality rate associated with respiratory syncytial virus infection was 2.2%. Few patients with the infection had life-threatening clinical features or concurrent serious illnesses.

The researchers wrote that an effective vaccine for children aged older than 2 months could substantially prevent the incidence of respiratory syncytial virus.

Nokes DJ et al. Clin Infect Dis. 2009;49:1341-1349.

It is estimated that there are about 150 million cases of pneumonia in children annually, with about two million deaths mainly in Africa and India. In addition to bacterial pneumonia, RSV appears to be one of the main causes of these illnesses. The authors attempt to quantify the contribution of RSV to the pneumonia burden of children in rural Kenya. By studying the cases of severe pneumonia admitted to the hospital and testing for RSV, they estimate the burden attributable to this virus. The infection, as in American infants, is largely in early infancy. A significant proportion of pneumonia illness is due to RSV. In general, RSV was more common in less severe pneumonia than in those who had RSV negative pneumonia. The authors did not attempt to determine how many of the infected children had bronchiolitis, which is the most characteristic clinical presentation in infancy. In contrast to the American experience, prematurity was not a major player. This may reflect the poorer survival of low birth weight infants in this population.

The authors present data to support the prevention of RSV by immunization. They do not indicate how many, if any, of these children had received influenza vaccine, which is another major cause of morbidity in childhood. An RSV vaccine is still a ways off. The original killed vaccine several decades ago worsened the clinical illness in recipients. More recent attempts to produce a vaccine have focused on a live intranasal vaccine, which has had variable efficacy. One of the significant side effects in very young infants is “stuffy nose”. This may seem trivial for those who do not take care of infants but babies are obligate nose breathers and for them it is a big deal. It is important to immunize early as significant morbidity occurs in those younger than six months. At the current time in the United States, infants at high risk, mainly those who are small or premature, are protected by passive immunization with a monoclonal antibody preparation. It certainly would be preferable to have a less expensive and more widely applicable vaccine. The quest continues.

- Philip Brunell, MD

Infectious Diseases In Children Editorial Board member