Ask the Experts: ACIP tackles range of vaccine topics at meeting

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Immunization Update

The following article is part one of a two-part series covering vaccine topics addressed at the October 2013 meeting of the Advisory Committee on Immunization Practice (ACIP). More topics will be covered in next month’s Immunization Update.

Influenza vaccine

The recent publication of the 2013–14 ACIP influenza recommendations included new vaccine strains, licensure of six new influenza vaccines, and clarification of egg allergies. Since the publication of the report, Flulaval Quadrivalent (ID Biomedical) was licensed and Flulaval Trivalent was approved for a new age indication (patients >3 years).

As of October 12, influenza activity was low, which is normal for this early in the influenza season. About 90% of the strains reported so far are type A. Influenza-like illness (ILI) activity remains low.

Vaccination coverage rates for the 2012–13 season were reviewed. A total of 134.9 million doses were distributed last season, with coverage rates of 57% in children, 41.5% in adults older than 18 years, and 66% in individuals 65 years or older. Rates were higher in all age groups.

A summary of the Fluzone High-Dose (Sanofi Pasteur) vaccine efficacy trial results was presented. The prelicensure trials demonstrated that the vaccine induced a statistically significantly higher antibody response against all three strains compared with regular-dose Fluzone vaccine. Fluzone High-Dose is indicated for adults 65 years or older, while regular-dose Fluzone is recommended for patients 6 months or older.

A study comparing the clinical efficacy of Fluzone High-Dose with Fluzone trivalent vaccine was presented. The study enrolled approximately 32,000 participants 65 years or older in 128 study sites over two influenza seasons. The study was designed to compare the efficacy with respect to laboratory-confirmed influenza caused by any influenza strain with the occurrence of protocol-defined ILI. Relative efficacy was 24.2% higher for Fluzone High-Dose (1.43% vs. 1.89% ILI). Slight improvement also was seen for pneumonia, hospitalizations, and cardiorespiratory episodes. Additional analysis and studies are under way.

Meningococcal vaccine

Three conjugated meningococcal vaccines have been approved in the United States. MenACYW-135-CRM (Menveo—Novartis) recently received an indication for age as early as 2 months (2 months to 55 years). The studies submitted for FDA approval were presented. The vaccine demonstrated effective blood titers and did not interfere with other vaccines given in the infant series. The GRADE analysis was similar to the other meningococcal vaccines. The working group decided that Menveo should be added as an option for vaccinating high-risk infants.

Pneumococcal vaccine

Many countries have implemented pneumococcal conjugate vaccine (PVC) in a three-dose schedule (compared with the four-dose schedule in the United States). CDC has been evaluating the incidence of invasive pneumococcal disease (IPD) in children since 2010 (when 13-valent PCV [PCV13] was licensed) and is observing a decline. Also, as a result of herd effect, IPD appears to be declining in adults. The vaccine effectiveness in one study against all IPD in children was 65%. However, if vaccine effectiveness is measured against the PCV13 serotypes in the vaccine, it climbs to 89%.

Because the World Health Organization recognizes a three-dose schedule as acceptable, the working group is discussing a reduction in the number of doses in the pneumococcal childhood series. We also are seeing a large decline in disease burden in the United States caused by serotypes in the vaccine. Looking at studies from other countries, the vaccine effectiveness ranged from 70% to 100% against vaccine-type IPD. The vaccines used in these studies included PCV7, -9, and -13. The four-dose series studies reported a vaccine effectiveness of 81% to 100%. No studies comparing three- and four-dose schedules have emerged. Differing types of studies (e.g., randomized controlled versus observational) and differing diseases (e.g., IPD, pneumonia, acute otitis media) are under way.

In conclusion, the three-dose PCV studies demonstrated effectiveness against IPD, pneumonia, and otitis media. The immunogenicity studies demonstrated that after the primary series, three doses are more effective than two, but this difference does not continue after the second year of life. Also, little difference was noted after the booster dose for the two-plus-one versus three-plus-one series. The same pattern was seen with nasopharyngeal carriage. However, the differences may not be meaningful because PCV7 serotypes rarely cause disease and the PVC13 serotype disease is disappearing. The herd effects are similar, so changes at the population level are not expected.

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