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December 7, 2017

Influenza Surveillance Update, 2016–2017 Season Review, and 2017–2018 Vaccine Update – Alicia Fry (CDC)

Alicia provided a summary of the influenza surveillance report from week 47, ending on November 25, 2017, vaccine effectiveness data, and a vaccine update for the current season.

Current Surveillance
Overall, influenza activity is increasing throughout the country. The percentage of respiratory specimens testing positive for influenza in clinical laboratories has been steadily rising over the last few weeks and is now at 7.2%. The majority of specimens (88.6%) tested at public health laboratories were influenza A, and 11.4% were influenza B. Influenza A H3 continues to be the dominant strain reported, though smaller numbers of influenza A (H1) and influenza B also have been reported. For the 2017–2018 season as a whole, 89.1% of influenza A specimens were H3. For the B viruses for which lineage information was available, 62.4% were B Yamagata. Since October, 277 viruses have submitted for antigenic and genetic characterization, and the majority have been antigenically and genetically similar to the reference virus for this season’s vaccine. There has been no antiviral resistance detected to date.

Nationwide, influenza-like illness (ILI) activity was at 2.3%, above the national baseline of 2.2%. Four HHS regions (Regions 1, 4, 6, and 7) were at or above their region-specific baselines. ILI information also is available on a state level, with activity summarized as high, moderate, low, or minimal. During week 47, 3 states (Louisiana, Mississippi, and South Carolina) reported high ILI activity, 1 state (Georgia) reported moderate ILI activity, 10 states reported low ILI activity, and 36 states and the District of Columbia reported minimal ILI activity. Data were insufficient to calculate an ILI activity level from Puerto Rico.

Information from the Influenza Hospitalization Surveillance Network (FluSurv-NET) indicates an overall hospitalization rate of 2.0 per 100,000 population. The highest rate (7.3 per 100,000) was among adults aged >65 years. When compared with prior seasons, the current hospitalization rate is similar to the levels in the 2014–2015 season.

Based on reports from the National Center for Health Statistics (NCHS) surveillance system available for the week ending November 11, 5.7% of deaths were due to pneumonia and influenza (P&I). This percentage is below the epidemic threshold of 6.5% for the week.

No influenza-associated pediatric deaths were reported during week 47. For the 2017–2018 season, the total number of reported pediatric deaths remains at five.

In terms of geographic spread of influenza within a state (characterized as widespread, regional, local, sporadic, or no activity) as reported by state and territorial epidemiologists, 4 states (Georgia, Louisiana, Massachusetts, and Oklahoma) reported widespread activity, 10 states and Guam reported regional activity, 24 states and Puerto Rico reported local activity, and 12 states, the District of Columbia, and the U.S. Virgin Islands reported sporadic activity.

Review of 2016–2017 Season
Alicia continued by providing an overview of the 2016–2017 season. During that season, there were approximately 602,000 influenza-associated hospitalizations. Similar high hospitalization levels are seen in the 2012–2013 and 2014–2015 influenza seasons, which also were predominantly H3N2 seasons, As recently published in the American Journal of Epidemiology, investigators are now using the burden of seasonal influenza data (looking at illnesses, medical visits, and hospitalizations) to develop a severity index to provide a comparison between differing seasons. The 2016–2017 season was considered to be of “moderate” severity.

Vaccine effectiveness (VE) in 2016–2017 was 42%. When stratified by subtype, the VE for influenza A was 34% and influenza B was 56%. From 2010–2011 to 2015–2016, an estimated 39,300 – 86,700 influenza hospitalizations were averted. Even when VE is low, such as in 2012–2013, over 60,000 hospitalizations were averted. VE was similar throughout the world during last season. Alicia noted that the reason VE is lower against H3N2 viruses is multifactorial, but egg adaptation changes in vaccine viruses likely play a role. This season’s influenza vaccine contains the same H3N2 vaccine component as last season.

2017–2018 Influenza Vaccine Update
The 2017–2018 ACIP Influenza Statement was published in the MMWR on August 25, 2017. A Background Document with additional references and a Summary of Recommendations are available on the ACIP web pages.

The principal changes and updates for 2017–2018 (see slide presentation for specific details) include:

  • Influenza vaccine composition
  • Several new licensures/licensure changes
  • Updated recommendations for Afluria (IIV3)
  • Extension of the recommendation that LAIV not be used.

Major items that are unchanged for 2017–2018 include:

  • There are many vaccine options, with no preferential recommendation
  • Dosing algorithm for children age 6 months through 8 years is similar to the last two seasons
  • Timing of vaccination – Before end of October
  • Egg allergy algorithm no longer printed in MMWR

A Summit member asked whether the cell-based or recombinant vaccines are likely to have a higher VE against H3N2 viruses this year. Alicia noted that, although many people are predicting this, CDC will be unable to measure this because there is not enough commercial use of these vaccines for it to be picked up in the surveillance networks. This year’s H3 component is from an original cell-grown virus, but the H1 and B components are from egg-propagated viruses which are placed into cells. This year the H3 component is “cell-cell,” so those changes that occur as the virus is adapting to the egg are not present for H3. One study from 2014–2015 suggested higher VE for recombinant vaccine, but it also has higher antigen dose, making it difficult to tease out the answer to this question from the data.

November 2017 Influenza Vaccination Coverage – Tammy Santibanez and Carla Black (CDC)

Tammy and Carla discussed results of November 2017 Influenza Vaccination Coverage Surveys.

CDC has just posted the national-level early season influenza vaccination coverage estimates for the general population of children and adults in the United States. Overall, this season’s coverage is similar to last year’s at this time for all age groups. Coverage for adults was 38.5%. Vaccination coverage among children was similar to 2016 totals in all age groups, with lower levels in older children. The opposite was true for adults, where coverage was higher with increasing age.

For all racial and ethnic groups, coverage was similar to the 2016–2017 season. The exception to this was among Hispanic adults, whose coverage was 7.7% lower than this time last year. The majority of adults and children were vaccinated at a doctor’s office.

Healthcare personnel (HCP) data were obtained from a non-probability internet panel survey. Coverage has not increased over previous seasons. By occupation, pharmacists had the highest coverage, followed by physicians, nurses, and other staff. Assistants and aides had the lowest coverage. By work setting, HCP working in hospitals had the highest coverage. Vaccination levels in HCP were highest among those whose employer required vaccination. The majority of HCP received influenza vaccinations in their workplace. Many HCP who were not vaccinated and who do not plan to get vaccinated were concerned about possible side effects. The most common reason given by HCP who were vaccinated was a desire to protect themselves from influenza.

The survey among pregnant women was also an internet panel survey. Because this year’s survey methodology was different than prior years, CDC will not be conducting comparisons with previous seasons. As of early November, flu vaccination coverage among pregnant women was 35.6%. Coverage was slightly higher among pregnant women who were over 25 years of age and those who were in their second or third trimester of pregnancy. Vaccination coverage was highest among women who are non-Hispanic “other” race. Coverage was higher among pregnant women with a college degree than women with a high school education or less, and it also was higher among pregnant women with private/military insurance.

As has been seen in prior seasons, a recommendation from a HCP has a significant influence on coverage. More than half (52.4%) of women who were offered vaccine by their provider were vaccinated, while only 26.1% were vaccinated if they received only a recommendation for vaccination from their provider. Most vaccinated women received their vaccine at their ob/gyn/midwife office. The most mentioned reason for being vaccinated was to protect their baby from the flu. The most common reason for not being vaccinated was the pregnant woman’s personal safety concerns. Women who intend to be vaccinated in the future stated they either hadn’t gotten around to receiving the vaccine yet or they wanted to wait until after their pregnancy.

Announcements

2018 Summit In-Person Meeting

The 2018 Summit in-person meeting will be held in conjunction with the National Immunization Conference (NIC) in Atlanta, Georgia. The NIC will be May 15–17, and the Summit will be May 17–18. Attendees are encouraged to participate in both events.

Information on registration and submission of poster abstracts for NIC is now available online. A separate registration and abstract submission process for the NAIIS meeting will be available online around the beginning of the year.

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