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After a poor matchup to circulating viruses in the 2014-2015 season, the Centers for Disease Control and Prevention (CDC) has released a new vaccine for this year, along with updated administration guidelines.
Last year’s influenza season was a harsh one, and there was criticism over the fact that the vaccine did not appear to match the influenza viruses that circulated.
As a result, the Centers for Disease Control and Prevention (CDC) says the vaccine has been updated based on samplings of last year’s circulating viruses.
The new influenza vaccine recommendations should not have a significant effect on clinical practice for pediatricians, says CDC spokesperson Ian Branam. The only real change, he says, is the lack of a preferential recommendation for children aged 2 to 8 years. An updated procedure is also provided for determining how many vaccine doses are needed in children aged 6 months to 8 years.
The updated recommendation states that children who received 2 or more doses of trivalent or quadrivalent influenza vaccine before July 1, 2015 should have 1 dose of the 2015-2016 influenza vaccine. Those that did not receive 2 or more doses of the trivalent or quadrivalent influenza vaccine before July 1, 2015 should receive 2 doses of the 2015-2016 vaccine.
Additionally, Branam says there is a new recommendation for the use of live attenuated influenza vaccine (LAIV), the nasal spray vaccine. The CDC and Advisory Committee on Immunization Practices (ACIP) no longer state any preference for LAIV over inactivate influenza vaccine (IIV), the flu shot, in children aged 2 to 8 years.
Influenza during the 2014-2015 season increased through late November into December, peaking in late December. The most prominent viruses included influenza A (H3N2) and influenza B strains later in the season, from February 2015 to May 2015.
Like previous years where influenza A was predominant, the 2014-2015 season saw high levels of influenza-related hospitalizations, especially for seniors, says CDC. To make matters worse, CDC acknowledges that the circulating influenza A viruses were different than those included in the season’s vaccine.
About half of the influenza A viruses were subtyped, and 99.6% were H3N2, while 0.2% were (H1N1)pdm09 viruses. Three variant influenza A viruses-1 H3N2v and 2 H1N1v-also were identified. As far as resistance to antiviral medications, CDC found that all the influenza B and influenza A (H3N2) viruses tested from the 2014-2015 season were sensitive to oseltamivir and zanamivir. All of the influenza B and more than half of the influenza A (H3N2) viruses were sensitive to peramivir. Out of 64 pH1N1 viruses tested, only 1 was resistant to oseltamivir and another to peramivir, CDC says. All influenza A (H1N1)pdm09 tested were sensitive to zanamivir. The CDC notes that high levels of resistance were found to the adamantanes (amantadine and rimantadine) among influenza A viruses-and they are not effective against influenza B viruses.
The 2014-2015 season also brought mortality rates that exceeded epidemic thresholds, according to CDC. Adult deaths primarily affected those aged 65 years and older, but pediatric patient deaths were also high for the season. The CDC says 141 confirmed influenza-associated deaths occurred across 40 states-14 in children aged younger than 6 months; 23 in ages 6 to 23 months; 22 in 2 to 4 years of age; 45 deaths in 5 to 11 years; and 37 in those aged 12 to 17 years. The median age of pediatric patients killed by influenza was 5.9 years, says CDC, and 109 of the pediatric deaths were associated with influenza A viruses compared to 29 with the influenza B viruses. The typical number of pediatric influenza-associated deaths ranges from 34 to 171 per season, except for the 2009 pandemic when 358 pediatric deaths were reported.
For this season, CDC is recommending influenza vaccination for everyone over 6 months of age with no contraindications. The vaccines should be given before the onset of influenza activity in the community-before October if possible-and be offered as long as influenza viruses are circulating. Immunity does not occur immediately-it takes 2 weeks to develop influenza antibodies following vaccine administration.
Children aged 6 months to 8 years should receive the trivalent or quadrivalent vaccine over 2 doses, with the first dose given as soon as the vaccine becomes available and the second dose about 4 weeks later.
The 2015-2016 trivalent influenza vaccines will contain hemagglutinin (HA) derived from an A/California/7/2009 (H1N1)-like virus; an A/Switzerland/9715293/2013 (H3N2)-like virus; and a B/Phuket/3073/2013-like (Yamagata lineage) virus. The makeup of this year’s vaccine reflects changes developed from observations of the 2014-2015 season, particularly in the influenza A (H3N2) virus and the influenza B virus.
Quadrivalent influenza vaccines will contain these vaccine viruses, plus a B/Brisbane/60/2008-like (Victoria lineage) virus.
A few updated vaccination methods are available, as well. Afluria (inactivated influenza vaccine) was approved by the US Food and Drug Administration (FDA) in August 2014 for intramuscular administration via the Stratis needle-free jet injector or sterile needle and syringe for adults aged 18 to 64 years. The Stratis injector is a reusable spring-powered device that injects the vaccine through a single-use sterile needle-free syringe into the deltoid muscle. Other inactivated influenza vaccines may be administered via needle and syringe only, says CDC.
In October 2014, FDA also approved an expanded age range for administration of Flublok (recombinant influenza vaccine). Previously only approved for adults aged 18 to 49 years, the vaccine is now available to children aged under 18 years.
Fluzone, approved by FDA in December 2014, is also available for adults aged 18 to 64 years and is expected to replace the previous trivalent Fluzone Intradermal.
The CDC’s ACIP is recommending that all children aged older than 6 months receive the influenza vaccine annually, and that vaccination should not be delayed to wait for a particular formulation of the vaccine if a suitable one is already available. The LAIV or IIV are appropriate for children aged 2 to 8 years with no special contraindications, says ACIP, and no preference between LAIV or IIV is expressed in those aged 2 to 29 years. The LAIV should not be used in those aged younger than 2 years or older than 49 years, according to ACIP.
Those with a severe allergy (e.g. anaphylaxis) to eggs or any component of LAIV, including egg protein, or after a previous dose of any influenza vaccine; have ever had a life-threatening reaction to influenza vaccinations; or are 2 through 17 years old and take aspirin or medicines containing aspirin should not receive LAIV.
In addition to the groups for whom LAIV is not recommended above, the “Warnings and Precautions” section of the LAIV package insert indicates that persons of any age with asthma might be at increased risk for wheezing after administration of LAIV. The package insert also notes that the safety of LAIV in persons with other underlying medical conditions that might predispose them to complications after wild-type influenza virus infection (e.g., chronic pulmonary, cardiovascular [except isolated hypertension], renal, hepatic, neurologic, hematologic, or metabolic disorders [including diabetes mellitus]), has not been established. These conditions, in addition to asthma in persons aged ≥5 years, should be considered precautions for the use of LAIV.
Despite samplings of last year’s viruses, CDC says it’s impossible to predict whether the 2015-2016 vaccine will be a close match to the season’s circulating viruses. Although efforts were made to update the vaccine based on last year’s results, the ever-changing nature of the influenza vaccine means that the makeup of the virus can change from 1 season to the next, even within the same season.
The full CDC advisory on this season’s influenza vaccine can be found here.