Prevention of Respiratory Syncytial Virus Infections
H. Prevention
The obvious choice for the prevention of serious RSV infection would be the development of a vaccine. However, a vaccine against RSV poses particular problems, (1) it would have to induce an immunity which is more durable than that seen after natural infection, and (2) it would have to be given at a very young age, when maternal antibodies may be present. The first vaccine produced was an inactivated vaccine which produced high levels of serum antibody but resulted in a more severe course of disease following infection by the wild virus. Several live attenuated vaccines have been tried but these were found to be too reactive, unstable or overly attenuated. A double temperature-sensitive mutant strain of RSV is being evaluated at the moment. Research is also being carried out on the F and G envelope glycoproteins as possible candidates for subunit vaccines.
Other means of protection for limited periods may be possible e.g. immunization of the mother before the birth of the infant or chemoprophylaxis of high-risk infants may be feasible. Prevention of the nosocomial spread of RSV infection is of prime importance, as many hospitalized infants have underlying conditions which make them susceptible to severe RSV infection. Of the infection control measures employed, hand washing is the most important. The routine use of gowns and masks has not been shown to be of additional benefit. The use of gowns may be advisable during periods of close contact in which the infant's secretions are apt to contaminate the clothing. Since RSV primarily infects via the eyes and nose, masks are of limited value. Eye-nose goggles have been reported to be of benefit.
Other possible infection control procedures include the isolation or cohorting of infected infants and assigning nursing personnel to care for either infected infants or uninfected infants, but not both simultaneously. During epidemic periods, the numbers of patient contacts and visitors should be limited. Elective admission of infants with high-risk conditions should be avoided during epidemic periods. Recognition and cleaning of objects contaminated with infant secretions should be carried out as soon as possible.
RSV Hyperimmunoglobulin
RespiGam has been approved by the FDA for the prevention of respiratory syncytial virus (RSV) disease in children under 24 months with a chronic lung disease called bronchopulmonary dysplasia or a history of premature birth. RespiGam is made from plasma taken from large numbers of normal, healthy individuals and contains a high concentration of protective antibodies against RSV. These antibodies do not prevent RSV infections but help protect children against the most serious consequences of RSV. RespiGam is given intravenously in five monthly doses, with the first dose given in November before the start of the RSV season. RSV outbreaks occur in the U.S. during the late fall, winter, and early spring. Data supporting the licensing of RespiGam was obtained in several clinical trials including one known as the Prevent trial. This randomized, placebo-controlled double-blind study included 510 patients with BPD less than two years old or children under six months old with a history of premature birth (less than 35 weeks gestation). RespiGam reduced the number of hospitalizations by 41% and time in the hospital by 53% in the Prevent trial. In addition, children required fewer days of supplemental oxygen during their hospital stays.
