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Past studies conducted in Australian and American families have demonstrated that alpha 2b interferon (IFN) is effective in preventing rhinovirus-associated illnesses in exposed family members. IFN had been used by intranasal application for 7 days after exposure (5 x 10(6) IU/day). We used the same approach but with only 5 days of spraying (5 x 10(6) IU on day 1 and 2.5 x 10(6) 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 required a dosage of at least 5 x 10(6) IU of IFN-alpha 2b.

Recombinant alpha-2b interferon was evaluated in two controlled trials, each lasting for 2 months or more, with different dose levels and schedules of administration. The first study was conducted during a period of transmission of type A (H1N1) and type B influenza. At 2.5 x 10(6) IU per day, no effect on influenza infection could be detected, but there appeared to be an effect on rhinovirus isolation. During the subsequent autumn 1.7 x 10(6) IU per day was found to have only a minimal effect on rhinovirus infection (efficacy from 22 to 27%). Under similar circumstances the preceding year, but with a daily dose of 3.0 x 10(6) IU, efficacy had been 76%. Since there was no evidence of change in rhinovirus strains circulating or their interferon susceptibility, this represented a dose-response relationship. It was possible to evaluate side effects in the 1,200 individuals involved. A lower dose was associated with lower frequency of symptoms of blood-tinged mucus. Persons using a placebo spray had a higher frequency of this side effect than an observed control. Using the spray 5 days a week was no less likely to produce symptoms than everyday use. Once-daily use was less likely to produce side effects than twice-daily use. There was no indication of sensitization when interferon was used for two separate periods of 4 weeks.

The safety, tolerance, and levels of drug in the nasal cavity produced by an ocular formulation of interferon were determined at four dosages in a placebo-controlled, double-masked trial. Interferon given by the ocular route was generally well tolerated, although a dose-related occurrence of subjective symptoms was detected.

In a double-blind, placebo-controlled study, patients with naturally occurring common colds of less than or equal to 48 h duration were randomly assigned to receive nasal sprays of recombinant alfa-2b interferon at 10 or 20 MU/day or placebo four times per day for 5 days. The 10-MU (n = 74), 20-MU (n = 74), and placebo (n = 72) groups had comparable frequencies of documented rhinovirus colds (50 to 65%) and mean durations of pretreatment symptoms (26 to 27 h). The median duration of colds tended to be longer in the 20-MU group (10 days) than the 10-MU group (8 days) or placebo group (8 days) (P = 0.06). In those with proven rhinovirus colds treated within 24 h, the median duration was significantly longer in the 20-MU group (9 days) than in the placebo group (6 days). No differences favoring interferon treatment were found in respiratory symptom scores or resolution of specific symptoms. On days 5 and 7, nasal washings from compliant subjects with proven rhinovirus colds yielded rhinoviruses more often in placebo (47 and 48%, respectively) than in interferon (15 and 16%, respectively) recipients (P less than 0.02), but no differences in new respiratory illness occurrence were observed in household contacts. Interferon recipients had significantly higher frequencies of blood in nasal mucus (16 to 18%) than did placebo recipients (4%) during treatment. Antibiotics for presumed secondary infections were given more often in the 20-MU group (11%) than in the placebo group (0%) (P less than 0.01). Nasal sprays of recombinant alfa-2b interferon were not an effective treatment for natural colds and were associated with toxicity.