Dr. MeissnerAlthough people of all age groups are susceptible to influenza, children experience the highest influenza attack rate. Complications, hospitalizations and deaths from seasonal influenza generally are greatest among people ages 65 years and older, children younger than 5 years (particularly those younger than 2 years) and people of any age who have certain medical conditions.
Since 2004 when reporting began, 37 to 171 influenza-associated pediatric deaths have been reported during each non-pandemic influenza season.
Which two of the following statements are false?
a) Women who are pregnant or within two weeks postpartum are at increased risk from influenza infection.
b) All children with egg allergy can receive influenza vaccine with no additional precaution other than those of routine vaccinations.
c) Maternal influenza immunization during pregnancy likely confers passive protection of an infant until at least 2 months of age.
d) Mortality in children with influenza B virus infection appears to be greater than that associated with influenza A virus infection.
e) The Academy and Centers for Disease Control and Prevention (CDC) recommend that intranasal influenza vaccine (LAIV4) may be used only in selected children and adolescents for 2016-’17.
f) Quadrivalent influenza vaccines have been demonstrated to offer greater protection against influenza infection than trivalent vaccines.
Answer: e and f are not correct
Because of low effectiveness against certain influenza A strains (influenza A(H1N1pdm09) in particular) for the last three influenza seasons, both the Academy and the CDC recommend that LAIV4 not be used in any setting during the 2016-’17 season. Although LAIV may be available, only an inactivated vaccine (IIV) should be used for children and adolescents. No preference is expressed by the Academy or the CDC for a quadrivalent vs. a trivalent vaccine (Pediatrics. 2016;138(4):e20162527, http://bit.ly/2d4337f).
Influenza may be caused by type A or type B viruses that often co-circulate during the influenza season. Influenza A viruses undergo unpredictable antigenic change, infect a broad range of avian and mammalian hosts, and periodically cause devastating epidemics. In contrast, type B viruses are less likely to undergo major antigenic change, are known to infect only humans and seals, and do not cause pandemics.
A recent report from Canada (Pediatrics. 2016;138(3):e20154643, http://bit.ly/2cOuoxG) evaluated 4,155 children ages 16 years and younger who were hospitalized at one of 12 pediatric referral centers with laboratory-confirmed influenza. Mortality was significantly greater for type B (1.1%) than for type A (0.4%) infection even after adjusting for age and health status. Among hospitalized, previously healthy children ages 10 years and older, requirement for intensive care was greater for those with type B infection.
Mortality among influenza-infected people older than 18 years of age may be associated with bacterial infections caused by Streptococcus pneumoniae or Staphylococcus aureus with a propensity to cause necrotizing pneumonia. Among people younger than 18 years of age, reports suggest that viral myocarditis rather than secondary bacterial infection may be a more important cause of death. Perhaps, this reflects immunity from widespread uptake of pneumococcal vaccines among children and adolescents.
Although most IIV vaccines are produced in eggs and contain trace amounts of egg protein (ovalbumin), recent data have shown that IIV is well-tolerated by recipients with a history of egg allergy of any severity. A history of egg allergy does not impart an increased risk of anaphylactic reaction to vaccination with IIV. A 2012 review of published data found no instances of anaphylaxis among 4,172 egg-allergic patients, 513 of whom had a history of severe egg allergy, after vaccination with influenza vaccine.
According to a Vaccine Safety Datalink study, the rate of anaphylaxis after IIV3 administration is about one per 1 million doses (10 instances in almost 7.5 million doses administered without other vaccines from 2009 to 2011). This rate of anaphylaxis is not different from that of other vaccines, including vaccines that do not contain egg protein.
Previously, a waiting period of 30 minutes after vaccination was recommended for patients with history of egg allergy. A recent study found that the onset of symptoms of anaphylaxis after receiving any vaccine began more than 30 minutes later in 21 of 29 cases. Because of this result, consideration of a waiting period of 15 minutes for all patients now is recommended after vaccination to reduce the risk of injury from syncope.
Influenza virus. Image coutresy of the Centers for Disease Control and Prevention.
A universal influenza vaccine that confers protection against multiple strains has been a goal for many years. One approach is based on the observation that changes occur frequently in the globular head of the surface proteins, neuraminidase and hemagglutinin (see image). In contrast, the stalks of the surface proteins are highly conserved. This plasticity in the protein's heads allows for mutations in the surface proteins but retains the biologic function of the stalk. A vaccine that contains the highly conserved epitopes found in the protein stalk might confer immunity against a variety of influenza strains.
Dr. Meissner is professor of pediatrics at Floating Hospital for Children, Tufts Medical Center. He also is an ex officio member of the AAP Committee on Infectious Diseases and associate editor of the AAP Visual Red Book.
