Influenza Guidelines Updated

The Advisory Committee on Immunization Practices (ACIP) has issued updated guidelines for prevention and control of influenza and published them in the July 17 Early Release issue of the Morbidity & Mortality Weekly Report. The 2008 recommendations include new and updated information since the 2007 recommendations by the Centers for Disease Control and Prevention's ACIP regarding the use of influenza vaccine and antiviral agents.

"Annual influenza vaccination is the most effective method for preventing influenza virus infection and its complications," write Anthony E. Fiore, MD, from the National Center for Immunization and Respiratory Diseases. "Influenza vaccine can be administered to any person aged >6 months (who does not have contraindications to vaccination) to reduce the likelihood of becoming ill with influenza or of transmitting influenza to others.... If vaccine supply is limited, priority for vaccination is typically assigned to persons in specific groups and of specific ages who are, or are contacts of, persons at higher risk for influenza complications."

Since the 2007 statement, key updates and changes in the 2008 guidelines include the following recommendations:

All children aged 5 to 18 years should receive annual vaccination beginning in the 2008 to 2009 influenza season, if feasible, but no later than the 2009 to 2010 influenza season.
Because children aged 6 months through 4 years (59 months) are at higher risk for influenza complications vs older children, annual vaccination of all children should continue to be a main focus of vaccination efforts.
Either trivalent inactivated influenza vaccine (TIV) or live, attenuated influenza vaccine (LAIV) should be used when vaccinating healthy persons aged 2 through 49 years (the 2007 recommendation was to administer LAIV to persons aged 5 - 49 years).
Vaccines should be used that contain the 2008 to 2009 trivalent vaccine virus strains A/Brisbane/59/2007 (H1N1)-like, A/Brisbane/10/2007 (H3N2)-like, and B/Florida/4/2006-like antigens.
The 2008 statement provides new information on antiviral resistance among influenza viruses in the United States as well as a summary of safety data for US licensed influenza vaccines.

If children aged 6 months to 8 years have not been vaccinated previously at any time with either LAIV or TIV, these children should receive 2 doses of vaccine, which are required for protection, separated by more than 4 weeks.

Children aged 6 months to 8 years who received only 1 dose in their first year of vaccination should receive 2 doses the following year.

Children younger than 5 years with possible reactive airways disease, such as recurrent or recent wheezing, should not receive LAIV. These children should receive TIV, as should persons at higher risk for influenza complications because of underlying medical conditions, children aged 6 to 23 months, and persons older than 49 years.

Although influenza A (H1N1) strains resistant to oseltamivir have been identified in the United States and in some other countries, oseltamivir or zanamivir continue to be the recommended antiviral agents to treat influenza because other influenza virus strains are still sensitive to oseltamivir, and resistance levels to other antiviral medications are still high.

Updated influenza vaccination recommendations for children and adolescents aged 6 months to 18 years are as follows:

Before or during the 2008 to 2009 influenza season, if feasible, but no later than during the 2009 to 2010 influenza season, vaccination should begin of all children aged 6 months to 18 years. Vaccination of all children aged 5 to 18 years is a new ACIP recommendation.
As providers and programs make the transition to routinely vaccinating all children and adolescents, children and adolescents at high risk for influenza complications should continue to be a focus of vaccination efforts. For these children, recommendations have not changed. Conditions putting children and adolescents at higher risk for influenza complication are as follows:
Ages 6 months to 4 years.
Chronic disorders of the pulmonary (including asthma), cardiovascular (except for hypertension), renal, hepatic, hematologic, or metabolic (including diabetes mellitus) systems.
Immunosuppression, including that caused by medications or by HIV.
Cognitive impairment, spinal cord trauma, seizure, or other neuromuscular disorders that could impair respiratory tract function or the handling of respiratory tract secretions or that could increase the risk for aspiration.
Use of long-term aspirin therapy increasing the risk for Reye's syndrome after influenza virus infection.
Residence in chronic-care facilities.
Pregnancy during the influenza season.

Although children younger than 6 months should not be vaccinated for influenza, household and other close contacts of children younger than 6 months, including older children, adolescents, and daycare providers, should be vaccinated.

Annual recommendations for adults have not changed, and annual vaccination against influenza is still recommended for any adult who wants to lower the risk of contracting influenza or transmitting it to others. Vaccination also is recommended for all adults at high risk, defined similarly to children at high risk and also including persons older than 50 years.

"Most studies find that vaccination reduces or minimizes health care, societal, and individual costs, or the productivity losses and absenteeism associated with influenza illness," the authors of the guidelines conclude. "Continued annual monitoring is needed to determine the effects on vaccination coverage of vaccine supply delays and shortages, changes in influenza vaccination recommendations and target groups for vaccination, reimbursement rates for vaccine and vaccine administration, and other factors related to vaccination coverage among adults and children. One of the national health objectives for 2010 includes achieving an influenza vaccination coverage level of 90% for persons aged >65 years and among nursing home residents; new strategies to improve coverage are needed to achieve these objectives."

Influenza is transmitted primarily from person to person via large-particle respiratory droplets. The incubation period before clinical symptoms of influenza varies between 1 and 4 days, but adults who are infected can shed the virus before the onset of symptoms. The amount of virus shed declines rapidly within 3 to 5 days of the onset of symptoms, but healthy adults can continue to shed the influenza virus up to 10 days after the onset of illness. Virus shedding can continue for weeks or months among individuals who are severely immunocompromised, and children can also shed the influenza virus for 10 or more days after the onset of symptoms of influenza infection.

Infection with influenza is an important public health issue, accounting for an annual average of 36,000 deaths in the United States from 1990 to 1999. The current recommendations from the ACIP focus on clinical measures to prevent infection with influenza.