Improving Efforts to Prepare for Influenza Epidemics

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Vaccine mismatch should be a focus of continued research, and there is also a need for further investigation regarding antiviral prophylaxis.
Vaccine mismatch should be a focus of continued research, and there is also a need for further investigation regarding antiviral prophylaxis.

The 2017 to 2018 influenza season may be 1 of the worst in recent years, with the greatest influenza-like illness (ILI) activity observed since 2009.1 On the heels of the seasonal peak, a paper published in BMJ explored options to improve preparation for influenza epidemics.2 The study authors reviewed the 3 main available approaches, as summarized here.

Vaccination. There is currently a major emphasis on vaccination, which the authors find "curious, because its effectiveness is disappointing." Because of the low annual incidence of clinically confirmed influenza, vaccination would result in a "drop from 2% to 1%, clinically imperceptible because of the much higher incidence of ILIs." A Cochrane Review of 90 reports, including 69 clinical trials with a combined 70,000 participants, found that the incidence of ILI symptoms in unvaccinated and vaccinated individuals was 15.6% vs 9.9%. Laboratory-confirmed influenza developed in 2.4% and 1.1% of these participants, respectively.3

There is inherent uncertainty regarding vaccine effectiveness as a result of antigenic drift, requiring annual revaccination with modified antigens, and antigenic shift, which results in little or no protection against the virus and increases the risk for pandemic. In addition, some findings suggest that repeated influenza vaccinations may lead to reduced vaccine effectiveness of the vaccine, although results have been mixed overall.4

For the 2017 to 2018 influenza season, the estimated effectiveness of the influenza vaccine is low. However, there is "no question that the vaccination reduced the severity of symptoms among recipients," Tara Vijayan, MD, an infectious disease specialist and assistant professor of medicine at the David Geffen School of Medicine at the University of California, Los Angeles, told Infectious Disease Advisor. For now, that observation is anecdotal, although she anticipates that it will be supported by hard evidence once the data from the season are analyzed.

Antivirals. The value of antiviral medications in influenza treatment is widely debated. In a 5-day illness, antivirals have been found to reduce symptoms by approximately one-half of a day, and "any effect on secondary infections or admissions to hospital, or on spread of the virus in an epidemic, remains uncertain," according to the BMC paper.2 After a review of evidence last year, the World Health Organization downgraded the status of oseltamivir from a "core" drug to a "complementary" drug on the WHO Model List of Essential Medicines.5

Hygiene. Results of another Cochrane Review support the effectiveness of physical interventions in limiting the spread of respiratory viruses.6 Hygienic measures including handwashing and face masks were shown to be highly effective, with surgical masks and N95 respirators demonstrating the most consistent protection (N95 respirators were noninferior to surgical masks). The numbers needed to treat with such methods are as low as 3 compared with a number needed to vaccinate of 71 for confirmed influenza and a number needed to treat of 33 and 51 (for oseltamivir and zanamivir, respectively) for reduction of symptomatic influenza with antivirals.3,7

Given such findings, the present authors contemplate why hygiene methods are not as widely promoted as vaccination or antiviral medications. "It would be facile only to blame industry promotion of drugs," they wrote, proposing that social norms likely exert a strong influence on the use or nonuse of such simple strategies. For example, wearing face masks in public is inconsistent with social norms in most countries. "Nor do such norms insist that people who are infectious stay away from work or school (instead, admiring them for 'soldiering on') or that mass gatherings (sports and cultural events) are cancelled."

They emphasize the importance of supporting low-technology policies, such the installation of hand hygiene dispensers on trains and public campaigns encouraging people to wear masks and cover their face when they cough. In the healthcare realm, these "cases are walking through all sorts of settings and clinics, so it's important to have clear signage [regarding hygiene recommendations] and basic protection available, such as masks...to prevent the spread of droplets," according to Dr Vijayan.

Routine testing for influenza is uncommon, which underscores the need to "make sure that frontline providers -- those in the trenches -- can recognize the symptoms of influenza-like illness in patients and themselves," she stated. "I believe we have a responsibility, as infectious disease specialists, to educate the broader medical community and encourage healthcare professionals to stay home." She notes that it is challenging to ensure the availability of an adequate healthcare workforce during an epidemic while ensuring that healthcare providers are protected and also not spreading the virus.

Vaccine mismatch should be a focus of continued research, and there is also a need for further investigation regarding antiviral prophylaxis. The Centers for Disease Control and Prevention has compiled a list of individuals at high risk for developing influenza-related complications, including young children, older adults, pregnant women, and people with various medical conditions, but the benefit is less clear for other groups.7 "Sometimes people without these risk factors do get infected and do very poorly," said Dr Vijayan. Additional studies should explore which types of patients may experience the most benefit from prophylaxis.8

References

  1. Centers for Disease Control and Prevention. Transcript for CDC update on flu activity. Published January 26, 2018. Accessed March 23, 2018.
  2. Del Mar C, Collignon P. How can we prepare better for influenza epidemics? BMJ. 2017;359:j5007.
  3. Demicheli V, Jefferson T, Al-Ansary LA, Ferroni E, Rivetti A, Di Pietrantonj C. Vaccines for preventing influenza in healthy adults. Cochrane Database Syst Rev. 2014;(3):CD001269.
  4. Ramsay LC, Buchan SA, Stirling RG, et al. The impact of repeated vaccination on influenza vaccine effectiveness: a systematic review and meta-analysis. BMC Med. 2017;15(1):159.
  5. Kmietowicz Z. WHO downgrades oseltamivir on drugs list after reviewing evidence. BMJ2017;357:j2841.
  6. Jefferson T, Del Mar CB, Dooley L, et al. Physical interventions to interrupt or reduce the spread of respiratory viruses. Cochrane Database Syst Rev. 2011;(7):CD006207.
  7. Jefferson T, Jones MA, Doshi P, et al. Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children. Cochrane Database Syst Rev. 2014;(4):CD008965.
  8. Centers for Disease Control and Prevention. People at high risk of developing flu–related complications. Updated January 23, 2018. Accessed March 23, 2018.
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