Influenza immunization strategy: It’s time for a change

Issue: December 2008

Too many of our nation’s children remain vulnerable to influenza every year because they do not get immunized.

Three years after the CDC first recommended influenza immunization for all children 6 to 23 months of age in 2005, the coverage rate in this age group is just 21%. We cannot settle for protecting just one in five children in this age group when safe and effective influenza vaccines are plentiful in the United States.

One simple way to increase immunization rates is to continue immunizing past November, historically a time when influenza immunization rates drop off sharply. There is no scientific reason for this drop; it is medically relevant and appropriate to continue providing influenza immunization into January and beyond. After all, influenza activity does not usually peak in the United States until February, and sometimes even later. Up to 30 million or more Americans will get influenza after the New Year, so it is clear that vaccines given in December and beyond can be of great benefit.

Influenza is serious, debilitating and even deadly

Influenza is an infection that hospitalizes more than 20,000 children younger than 5 years of age each year, and countless more older children. These are probably underestimates. Data from the CDC’s New Vaccine Surveillance Network show that physicians are misdiagnosing more than 70% of children with laboratory-confirmed influenza in both inpatient and outpatient settings.

Although influenza infection is most serious at the extremes of age, with the very old at the highest risk of influenza-related mortality, that doesn’t mean children are unaffected or that we should concede even one case of vaccine-preventable death in a child as acceptable. During the particularly severe 2003 to 2004 season, 153 influenza-related deaths in children were reported ad hoc. Since then, pediatric influenza-related mortality has been designated as reportable.

Reports of influenza-related deaths in children have been lower in subsequent seasons; 87 were reported last season. But we are seeing a troubling trend — a rise in methicillin-resistant Staphyloccocus aureus co-infection in children dying with influenza. Forty percent of the pediatric influenza-related fatal cases tested for bacterial infection last year had Staphylococcus aureus co-infection; 21% had MRSA. As recently as 2004 to 2005, the proportion of children with influenza and S. aureus co-infection was just 2%.

Expanded CDC and AAP recommendations

Starting this year, we have a universal recommendation for influenza immunization of all children 6 months through 18 years of age. This latest expansion, which includes school-aged children, has added roughly 30 million young people to the rolls of those we should immunize annually. It will not be easy, but very little of merit ever is.

The new recommendation was made because evidence shows that influenza has substantial adverse effects among school-aged children and their contacts. Influenza leads to increased school absenteeism, antibiotic use and medical care visits among children, and lost work time among parents and caregivers. School-aged children have the highest rates of infection, so the possibility exists that sufficient immunization coverage in this population also may yield herd-immunity benefits.

The direct benefits of influenza immunization are not available to everyone. Our youngest children (those younger than 6 months of age) cannot receive influenza vaccine or antiviral prophylaxis. It is essential to protect these most vulnerable infants by immunizing everyone who cares for them (“cocoon strategy”). Parents, siblings, grandparents, out-of-home caregivers and anyone else who comes in close contact with these infants should be given influenza vaccine. This, of course, includes me and every other healthcare professional.

Healthcare professionals have dual responsibilities

To meet our professional responsibility related to influenza immunization, we must do two things. First, we must get immunized ourselves. For pediatricians, whether in the hospital or outpatient setting, immunization is easy and often cost free. Only 42% of healthcare providers countrywide have received influenza vaccine during the past two seasons; hopefully, this rate is higher among pediatricians.

When we immunize ourselves, we reduce the risk of passing this highly contagious virus on to patients in our care. We also reduce the risk that we will get sick and be unable to work during a time when the healthcare system needs us most. And we set a good example, which brings me to our second responsibility: recommending the vaccine. With every passing year, it seems we have more responsibilities and less time to meet them. But again, that does not relieve us of our professional responsibility to do so. In this case, we must act because we are in the best position to make a difference.

Time and again, consumer surveys show that patients look to us for advice, and will follow that advice. In a recent survey of more than 2,000 American adults by the National Foundation for Infectious Diseases, 70% said they would get an influenza vaccine if their healthcare provider recommended it.

Extending our immunization efforts throughout the season

It is time to recognize that the old standard, that is, immunizing in October and November only, will not get the job done. We have many more people to reach every season, and we have a much larger supply of vaccine (~150 million doses) than ever before. While we need to increase our efforts within the “traditional” immunization months, we clearly need more time to deliver vaccines, raise rates, and protect more Americans, including our children. This also will allow us the opportunity to fully immunize those children younger than 9 years who require two doses of influenza vaccine if they have not been previously immunized.

It only takes about two weeks to develop immunity after influenza immunization, and since influenza cases usually continue in this country until early spring — and indeed cases do not even peak until around February in most years — immunizing throughout the winter months is warranted. Sure, it would be best to immunize everyone before even a single case of influenza occurs in a given season, but that is not likely to happen anytime soon; and because so many millions of cases will happen after the New Year, the medical relevance of influenza immunization in December and later is not debatable.

One preventable death is too many

The CDC and the Advisory Committee on Immunization Practices recommend that all children 6 months through 18 years of age get immunized every year to protect them from the serious morbidity and mortality associated with influenza. Widespread pediatric immunization also may help reduce virus transmission to other vulnerable members in our communities. But we only realize these benefits if we actually administer vaccines.

There has been a lot of media attention recently as to the effectiveness of influenza vaccine. The year-to-year variation in circulating influenza strains makes the “match” to the influenza vaccine better or worse. For example, last year the match was only 40% however, a 44% chance of being protected certainly beats zero. So far this year, WHO reports a 99% to 100% match between strains circulating in the southern hemisphere and the 2008 to 2009 influenza vaccines. With this kind of match, we are likely to have a vaccine that approaches 90% protective efficacy.

Influenza vaccines have excellent safety profiles, they are effective, and in most cases cost-effective or even cost saving. In the past several years, and into the foreseeable future, vaccine supply will be plentiful. Protect more of your patients by 1) immunizing yourself, 2) recommending vaccine to all of your patients 6 months-18 years of age, and 3) continue to give influenza vaccine now and well into the new year.

For more information:

Carol J. Baker, MD, is the moderator for the Childhood Influenza Immunization Coalition, www.PreventChildhoodInfluenza.org and a professor of pediatrics, molecular virology and microbiology at Baylor College of Medicine in Houston, Texas.