Ineffectiveness of postexposure prophylaxis of rhinovirus infection with low-dose intranasal alpha 2b interferon in families

Past studies conducted in Australian and American families have demonstrated that alpha 2b interferon (IFN) is effective in preventing rhinovirus-associated illness in exposed family members. IFN had been used by intranasal application for 7 days after exposure (5 x 10⁶ IU/day). We used the same approach but with only 5 days of spraying (5 x 10⁶ IU on day 1 and 2.5 x 10⁶ IU on each subsequent day). This amount has been effective in studies involving seasonal prophylaxis. During the study period, a total of 178 rhinoviruses were isolated from the 199 enrolled families in Tecumseh, Mich. There were 434 courses of IFN use and 434 courses of placebo use. Although rhinoviruses were less frequently isolated from those using IFN than those using the placebo, no differences favoring IFN treatment could be found in any of the symptomatic episodes. In fact, more episodes were observed in IFN recipients than in placebo recipients, although the differences were not statistically significant. Additionally, there was no evidence of modification of the severity of episodes of illness. It was concluded that prevention of rhinovirus illness episodes postexposure requires a dosage of at least 5 x 10⁶ IU of IFN-α(2b).