Posted 08/23/2007 Carrie M. Shuler, DVM, MPH
The US Centers for Disease Control and Prevention (CDC) recently updated recommendations for use of the influenza vaccine and antiviral agents. The revised guidelines (“Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices [ACIP], 2007”) were published in the June 29, 2007 Early Release issue of the Morbidity and Mortality Weekly Report.
A number of the updated recommendations concern infants and children. Carrie M. Shuler, DVM, MPH, Medical Epidemiologist, Georgia Division of Public Health, Notifiable Disease Epidemiology Section, Atlanta, Georgia, is lead author of a recently published study that evaluated influenza vaccine effectiveness among infants and young children. The study included 290 case children with laboratory-confirmed influenza age-matched 1:2 with control children. Peggy Keen, PhD, FNP, Editorial Director, Medscape Public Health & Prevention, spoke with Dr. Shuler about both child-specific changes in the 2007 guidelines and relevant findings from her vaccine effectiveness investigation.
Medscape: Would you please provide an overview of the changes and specific recommendations in the 2007 influenza guidelines that pertain to infants and children?
Dr. Shuler: Certainly. The recommendations still indicate that any child 6 months of age or older should be vaccinated for influenza. Vaccination is specifically recommended for certain children, including all of those who are 6-59 months of age; children with certain medical conditions, such as asthma; and children who have contact with persons who are at high risk for influenza complications. In particular, this includes children who are in contact with infants younger than 6 months of age who can’t be vaccinated and with persons older than age 50 who may have higher rates of complications secondary to influenza infection.
The 2007 ACIP recommendations also reiterate previous recommendations that persons, including all school-age children who want to reduce the risk of becoming ill or transmitting influenza to others, should be vaccinated. This is especially important for household contacts; therefore, parents, siblings, and grandparents having contact, and care providers of infants younger than 6 months of age, should be fully vaccinated.*
They also reiterated that previously unvaccinated children less than age 9, for whom the vaccine is recommended, should receive 2 doses of vaccine when being immunized against influenza for the first time. Healthy children 5 years of age or older can receive the live attenuated vaccine, with doses separated by at least 6 weeks or more. Administration of the trivalent inactivated influenza vaccine, recommended for those aged 6 months or older, needs to be separated by at least 4 weeks.
The main change in the 2007 recommendations is that infants and children aged 6 months to 8 years who have not been previously vaccinated need to receive 2 doses of age-appropriate vaccine within the same season, followed by single-dose vaccine in subsequent years. Children who received only 1 dose of vaccine in the first year will also need 2 doses in the second year. Then, in subsequent years, they should receive just 1 dose of influenza vaccine.
Medscape: You are the lead author of a recently published study that assessed the influenza vaccine effect among children age 6-59 months, conducted during the 2003-2004 influenza season. Could you provide an overview of the study and then discuss findings, especially with respect to the significance of data relative to the 2007 childhood chemoprophylaxis recommendations?
Dr. Shuler: Our study showed that the influenza vaccine — we looked specifically at trivalent inactivated vaccine — provided protection against medically attended, laboratory-confirmed influenza among infants and children aged 6-23 months, and those 24-59 months. The study was unique in that it was conducted during a season with a suboptimal match between vaccine and the circulating influenza strain — 2003-2004. And in Georgia, where the study took place, the season was very early. We had cases beginning in October, whereas the usual influenza season usually peaks around January-February.
We were able to show that the benefit was measurable among fully vaccinated children — those who had received their appropriate 2 doses of vaccine. They received a benefit to that vaccination when compared with unvaccinated children; the estimated decreased risk for medically attended influenza was 52% for children aged 6-23 months, and 45% for those aged 24-59 months.
Our study also showed that older children, those approximately aged 24-59 months, benefited from partial vaccination; these were kids who became ill at 14 days or more after receiving 1 of their 2 recommended doses. But, we found no vaccine effectiveness with partial vaccination for the youngest subset, those 6-23 months of age.
Our results provide support for recommendation for complete influenza vaccination of infants and children, and strengthen the evidence of the vaccine’s ability to greatly reduce the burden of disease among the 6- to 59-month-old age group — even in a year when the vaccine and circulating strains were not optimally matched.
Medscape: The authors of the CDC guidelines state: “Estimated vaccination coverage remains less than 50% among certain groups for whom routine annual vaccination is recommended including infants and young children.” Are there approaches you have found helpful, or any suggestions you may have for increasing the influenza immunization rate among infants and young children? These approaches are especially important because now many children will need 2 immunizations during the same influenza seasons rather than just a single vaccination.
Dr. Shuler: This is always a challenge, making sure that children are fully vaccinated prior to the start of the season. It is very important to remember that although the season typically peaks in January-February, people can continue to get vaccinated throughout the winter months and year round; this doesn’t have to just take place in October or September. So it is important that pediatricians and child immunization providers provide influenza vaccine and schedule clinics throughout the entire season, not just during the fall months when the latest vaccine is first distributed.
I think that administration of influenza vaccine should always be encouraged, even during routine healthcare visits. Any opportunity when a child is going to access care, it is appropriate to discuss the benefits of immunization with family members or child caregivers at that time. It is always important to continue providing valuable information — in the media, in publications about the safety and effectiveness of the vaccine — so that people are knowledgeable about the benefit not only for the children, but for other people who could be exposed. Also, other benefits of immunization, such as parents not missing time from work if their child is home sick, should be stressed.
Medscape: So start immunization early and remind of the importance often. Is there anything else related to the 2007 guidelines or about childhood influenza in general that you would like to share with Medscape’s readers?
Dr. Shuler: I think it is really important to reiterate that children — young children, especially those under age 2 — are at a high risk for hospitalization if they contract influenza, and for other related complications. Additionally, children up to age 5 often require medical care visits to health clinics or emergency departments. So parents and care providers who want to decrease their child’s risks for influenza should get that child vaccinated and should get vaccinated themselves. It’s also imperative to make sure that infants and children are fully vaccinated appropriately for their age and the season. This will not only reduce the risk in the child, but also reduce the chances that this child will expose others who might be even more vulnerable to influenza complications, such as infants younger than 6 months of age who can’t get vaccinated, or for older persons.
I think our study contributed further evidence that vaccination is the most effective way for preventing influenza virus infection — and in children, in particular, potentially severe complications. Our study showed that even during an influenza season when the vaccine match was not optimal, vaccine provided a substantial benefit to children 6-59 months of age who got their recommended number of doses.
Medscape: Thank you, Dr. Shuler, for talking today with Medscape.
*Influenza vaccines are not approved by US Food and Drug Administration (FDA) for infants younger than 6 months of age. Trivalent influenza vaccine is approved for persons aged 6 months or older, including those with high-risk conditions, whereas live attenuated influenza vaccine is approved for use only in healthy, nonpregnant persons aged 5-49 years.