HealthDay News — Less than half of Americans have received a flu vaccine so far this season, which might be a bad sign for a season that could be potentially severe, according to a report issued by the United States Centers for Disease Control and Prevention (CDC).

Only 39.7% of adults and 42% of children had received the flu vaccination through mid-November, results of a telephone survey conducted by the CDC indicate. Those numbers are comparable with vaccination rates last year at this time.

Health-care workers may face an uphill battle promoting the flu vaccine, however, since this year’s vaccine is only partially effective. The CDC warned that H3N2, a strain of influenza, appears to be circulating most widely early this season. About half of the H3N2 viruses detected by researchers so far appeared to have mutated. The mutation means that this year’s flu vaccine will likely only provide partial protection against H3N2.

CDC officials are urging the public to get the flu vaccine even though it may not be as effective against the mutated H3N2 strain.

Although the CDC did not observe any racial or ethnic differences in flu vaccination coverage so far this season, other studies have found lower coverage among Hispanic and non-Hispanic black adults. Clinicians should strongly encourage flu vaccination among these demographics.

Health-care providers can enhance efforts by recommending the flu vaccine to all patients, as patients are more likely to get vaccine when their providers give a strong recommendation, noted the agency.