Adamantanes have been used to treat influenza A virus infections for more than 30 years. Previous surveillance studies have identified a low incidence of resistance to amantadine and rimantadine among circulating influenza virus strains. However, it has been 10 years since the last comprehensive global study of resistance to these drugs was published.
In the largest study of adamantane resistance to date, Rick Bright (Centers for Disease Control and Prevention, Atlanta, GA, USA) and colleagues screened 7000 influenza A isolates for gene mutations known to confer drug resistance. They found that drug resistance increased from 0.4% in 1994-1995 to 12.3% in 2003-2004. They also found that 61% of resistant viruses isolated since 2003 were from people in Asia. Some Asian countries had drug resistance frequencies exceeding 70%.
Dr Bright comments: "We were alarmed to find such a dramatic increase in drug resistance in circulating human influenza viruses in recent years. Our report has broad implications for agencies and governments planning to stockpile these drugs for epidemic and pandemic strains of influenza…With the increasing rates of resistance shown here, amantadine and rimantadine will probably no longer be effective for treatment or prophylaxis in the event of a pandemic outbreak of influenza." (Quote by e-mail; does not appear in published paper)
See accompanying comment.
Contact: Rick Bright, Centers for Disease Control and Prevention, Atlanta, GA, USA. T) (404) 639-2898 rbright@cdc.gov
EMBARGO: 00:01H (London time) Thursday September 22, 2005. In North America the embargo lifts at 6:30pm ET Wednesday September 21, 2005.
FLU VACCINES HAVE MODEST EFFECTIVENESS IN ELDERLY PEOPLE
Vaccines against influenza are modestly effective for elderly people in long-term care facilities, but for those in the community their effectiveness is even less, according to a study published online today (Thursday September 21, 2005) by THE LANCET.
In 2000, 40 of the 51 developed countries or rapidly developing countries recommended vaccination for all individuals aged 60-65 or older. Tom Jefferson (Cochrane Vaccine Field, Rome, Italy) and colleagues identified and assessed 64 comparative studies of the effectiveness of influenza vaccines in individuals aged 65 years or older.
Combining data from 15 studies, they found that in elderly individuals living in the community, inactivated influenza vaccines were not effective against influenza-like illnesses, influenza, or pneumonia but prevented up to 30% of hospitalisations for pneumonia. Combining data from twenty-nine studies, they found that in elderly individuals in long-term care facilities, inactivated influenza vaccines prevented up to 42% of deaths caused by influenza and pneumonia.
Dr Jefferson concludes: "We need a more comprehensive and perhaps more effective strategy in controlling acute respiratory infections, relying on several preventive interventions that take into account the multi-agent nature of infectious respiratory disease and its context (such as personal hygiene, provision of electricity and adequate food, water and sanitation)". (Quote by e-mail; does not appear in published paper)
See accompanying comment.
Contact: Dr Tom Jefferson, Cochrane Vaccines Field, Via Adige 28a, 00061 Anguillara, Sabazia, Roma, Italy. T)+39 06 999 00 989/+39 32 92025051 toj1@aol.com
Journal
The Lancet