Yearly Flu Hospitalizations by Age Cohort – CDC FluView
Showing 2009-10 & 2013-14 Hitting ages 18-64 unusually hard
Despite reduced VE (Vaccine Effectiveness) estimates in recent years, and a production schedule that requires predicting – 6 months in advance – what flu strains will dominate in the upcoming flu season, we continue to see evidence that most years the seasonal flu shot manages to convey a fairly decent level of protection against influenza.
Despite the mantra of the CDC, and other public health organizations, urging people to get the yearly jab, only just over 1/3rd of adults (aged 18-64) got the flu shot last year (see TFAH Report Finds Low Uptake Of Flu Shots Among Young Adults).
This year, we are seeing the pH1N1 strain dominate for the first time since 2010, and as it did in 2009, it appears to be targeting younger adults harder than usual. As a result, we’ve seen reports of an uptick in ICU hospitalizations, and deaths, among younger adults across the nation this winter.
Which brings us to a research letter, published yesterday in the American Journal of Respiratory and Critical Care Medicine, that finds – between November 2013 and January 8th, 2014 – a `high number of otherwise healthy individuals with critical illness requiring care in the ICU. Most patients who required ICU level care were not previously vaccinated.’
Jelena Catania, Loretta G Que, Joseph A Govert, John W Hollingsworth, and Cameron R Wolfe
While most of this letter is behind a pay wall, we have a press release from Duke University, with some of the details. First an excerpt, after which I’ll return with more.
DURHAM, N.C. – A snapshot of patients who required care at Duke University Hospital during this year's flu season shows that those who had not been vaccinated had severe cases and needed the most intensive treatment.
In an analysis of the first 55 patients treated for flu at the academic medical center from November 2013 through Jan. 8, 2014, Duke Medicine researchers found that only two of the 22 patients who required intensive care had been vaccinated prior to getting sick.
The findings were published online in Monday, Feb. 10, 2014, in the American Journal of Respiratory and Critical Care Medicine.
"Our observations are important because they reinforce a growing body of evidence that the influenza vaccine provides protection from severe illness requiring hospitalizations," said lead author Cameron Wolfe, M.D., assistant professor of medicine at Duke. "The public health implications are important, because not only could a potentially deadly infection be avoided with a $30 shot, but costly hospitalizations could also be reduced."
Wolfe said this year's flu season was marked by hospitalizations of previously healthy young people, with a median age of 28.5 years. Among those who were hospitalized at Duke, 48 of the 55 were infected with the H1N1 virus that caused the 2009 pandemic. That outbreak also hit young adults particularly hard.
This research also found a high rate of failure of the rapid flu test (something we’ve discussed before in MMWR: Evaluating RIDTs and No Doesn’t Always Mean No) which has led to delays in starting antiviral treatment for some patients.
The authors conclude:
Together, our observations during this influenza season support a high prevalence of the H1N1 virus affecting young adults and requiring ICU care, high false negative rates of rapid flu tests, and delay in starting antiviral treatment," Wolfe said. "Added to the finding of very low vaccination rates among both hospitalized and ICU admissions, our observations support previous findings that vaccination reduces the severity of disease and vaccinations should be encouraged as recommended by the U.S. Centers for Disease Control and Prevention."
While the effectiveness of the seasonal flu shot has often been oversold, I certainly get one every year, and urge others to do the same.
Not because it is guaranteed protection, but because – like wearing a seatbelt in a vehicle – it improves your odds of a good outcome.
And despite disappointing VE numbers (see CIDRAP: A Comprehensive Flu Vaccine Effectiveness Meta-Analysis) - particularly among the elderly ( see PLoS One: Limited Effectiveness Of Flu Vaccines In The Elderly & BMC Infectious Diseases: Waning Flu Vaccine Protection In the Elderly) - we continue to see evidence of benefit from the shot, even if full protection isn’t conveyed to the recipient.
In 2011, NFID - the National Foundation for Infectious Diseases - convened a group of experts to address the issues of influenza and the elderly. From that panel a 5-page brief has emerged, called: Understanding the Challenges and Opportunities in Protecting Older Adults from Influenza.
Although the elderly generally see less protection from the flu vaccine, older individuals may still mount a robust immune response. In populations 65 and older, the brief points out that:
- Hospitalization rates for influenza and pneumonia are lower in community-dwelling adults who received the seasonal influenza vaccine.
- Immunization is associated with reduced hospitalization of older patients for cardiac, respiratory, and cerebrovascular diseases.
While the goal of vaccinating the younger population is to prevent infection, the authors point out that:
- . . . the goal in older adults is to prevent severe illness, including exacerbation of underlying conditions, hospitalization, and mortality.
Similarly, over the past couple of years, we’ve seen studies suggesting the flu vaccine may reduce the risk of heart attack and stroke (see JAMA: Flu Vaccine and Cardiovascular Outcomes & Study: Flu Vaccine May Reduce Heart Attack). Not a slam dunk, but intriguing nonetheless.
There is obviously a great need for better, and faster to market, flu vaccines. A topic that was well addressed back in 2012 by CIDRAP: The Need For `Game Changing’ Flu Vaccines.
But until they can be developed - the flu shots we have – when coupled with good `flu hygiene’ (washing hands, covering coughs, staying home when ill) remain the best preventative actions you can take against the flu.
And this year’s flu season shows that being young, and healthy, is no reason to avoid getting the shot.