By Staff

This week marks the official start of “flu season” for 2018-2019.

Last flu season was one of the worst on record and its about to start again. The season runs through fall and winter but usually peaks sometime after December but before February is over. While the peak usually happens within those months, the season can run late and into the springtime, sometimes as late as May, according to the Centers for Disease Control.

U.S. health officials are trying to increase the rate of flu vaccinations this year after a severe outbreak last season killed a record number of children and led to spot shortages of antiviral medications like Tamiflu.

In a panel hosted by the National Foundation for Infectious Diseases and the Centers for Disease Control and Prevention in Washington on Thursday, Surgeon General Jerome Adams took a nasal vaccine -- an effort, he said, to make flu prevention "go viral." The lighthearted demonstration was accompanied by grim statistics from the 2017-18 flu season: 80,000 deaths overall, including 180 children.

"I'm tired of hearing people say, 'Well, I didn't get sick and I didn't get the flu shot.' Or, 'I don't like it, my arm hurts,'" said Adams. "Those 80,000 people who died last year from the flu, guess what? They got the flu from someone. So it's critically important that we impress upon folks that it is not just for them. It's their social responsibility to get vaccinated."

The vaccine is expected to be more accurate this season, and influenza activity in the Southern Hemisphere has been unremarkable so far -- a good sign for the U.S. and Canada. But health officials at the briefing said it was too early to make a prediction.

"I would get the vaccine now and you don't have to worry about whether it's a mild or a severe season," said William Schaffner, NFID medical director.

The U.S. faced the most severe seasonal flu outbreak across all age groups since at least 2003 last season, according to CDC data. It led to 900,000 confirmed hospitalizations. So many people caught the flu that some hospitals and pharmacies across the U.S. ran out of antiviral drugs, Alabama declared a state of emergency and a school district in Arkansas closed all 10 of its schools.

"It really exposed how vulnerable we are," said Amesh Adalja, a senior scholar at Johns Hopkins University Center for Health Security. "It seems like we're in a better position this year. But it's the flu and it can do a lot of tricky things, so we won't know for sure until the season begins in earnest."

Each year, vaccines are produced in accordance with the CDC's predictions for the types of viruses most likely to circulate during flu season. Those predictions can be wrong, of course, but even when they are right vaccines can be mismatched to circulating viruses. Last winter, the U.S. vaccine was only 25 percent effective against the unexpected emergence of the H3N2 strain, or 36 percent effective overall, according to the CDC.

About 40 percent of U.S. residents received a seasonal flu vaccination last year. About 80 percent of the children killed hadn't received a shot. Vaccines significantly reduce a person's chances of catching the flu and spreading it to the most vulnerable people around them, such as the elderly. Even if someone does catch the flu after getting the vaccine, symptoms are likely to be less severe.

It can take about two weeks for the body to form antibodies to fight the flu after the vaccine is administered, according to the CDC.

While it’s recommended to be vaccinated by the end of October that doesn’t mean those who miss that timeframe shouldn’t get their vaccine, says the CDC. The vaccine can still help protect people who get it later in the season and can help prevent spreading the flu further.

In addition to getting the vaccine, people should stay home if they get sick and be sure to wash their hands to stop the spread of germs. “While flu spreads every year, the timing, severity, and length of the season varies from one season to another,” the CDC said.

Some employers and schools offer the flu vaccine each year while other places have drives where they offer free vaccines to those who need them. Additionally, health clinics and even some pharmacies and stores like Walgreens, CVS and Target offer the vaccine. For those with insurance, the vaccine is usually covered, for those without insurance, it can usually cost anywhere from $40 to $60.

The flu shot is recommended for most people six months of age and older, and especially for those at risk of flu complications, that can be deadly. The American Academy of Pediatrics announced that children over six months of age should get their vaccine as soon as possible.

The vaccine is also recommended for those at risk for complications include the elderly, the young, those with respiratory problems and people with weak immune systems, according to the CDC. There are different forms of the vaccine and some are more highly recommended for certain groups than others.

What was the 2017-2018 flu season like?

The 2017-2018 influenza season was a high severity season with high levels of outpatient clinic and emergency department visits for influenza-like illness (ILI), high influenza-related hospitalization rates, and elevated and geographically widespread influenza activity for an extended period. In 2017, CDC began using new methodology to classify seasonal severity and applied the methodology to the 2003-2004 through 2016-2017 seasons. The 2017-18 season was the first season to be classified as a high severity across all age groups.

When did the 2017-2018 flu season peak?

During the 2017-2018 season, influenza-like-illness (ILI) activity began to increase in November, reaching an extended period of high activity during January and February nationally, and remained elevated through the end of March. ILI peaked at 7.5%, the highest percentage since the 2009 flu pandemic, which peaked at 7.7%. Influenza-like illness (ILI) was at or above the national baseline for 19 weeks, making the 2017-2018 season one of the longest in recent years.

How many people died from flu during the 2017-2018 season?

While flu deaths in children are reported to CDC, flu deaths in adults are not nationally notifiable. In order to monitor influenza related deaths in all age groups, CDC tracks pneumonia and influenza (P&I)-attributed deaths through the National Center for Health Statistics (NCHS) Mortality Reporting System. This system tracks the proportion of death certificates processed that list pneumonia or influenza as the underlying or contributing cause of death. This system provides an overall indication of whether flu-associated deaths are elevated, but does not provide an exact number of how many people died from flu.

During the 2017-2018 season, the percentage of deaths attributed to pneumonia and influenza (P&I) was at or above the epidemic threshold for 16 consecutive weeks. During the past five seasons, the average number of weeks this indicator was above threshold was 11 (range of 7 to 15 weeks). Nationally, mortality attributed to P&I exceeded 10.0% for four consecutive weeks, peaking at 10.8% during the week ending January 20, 2018.

As it does for the numbers of flu cases, doctor’s visits and hospitalizations, CDC also estimates deaths in the United States using mathematical modeling. CDC estimates that from 2010-2011 to 2013-2014, influenza-associated deaths in the United States ranged from a low of 12,000 (during 2011-2012) to a high of 56,000 (during 2012-2013). Death certificate data and weekly influenza virus surveillance information was used to estimate how many flu-related deaths occurred among people whose underlying cause of death on their death certificate included respiratory or circulatory causes. For more information, see Estimating Seasonal Influenza-Associated Deaths in the United States and CDC’s Disease Burden of Influenza page.

How many children died from flu during the 2017-2018 season?

As of August 25, 2018, a total of 180 pediatric deaths had been reported to CDC during the 2017-2018 season. This number exceeds the previously highest number of flu-associated deaths in children reported during a regular flu season (171 during the 2012-2013 season). Approximately 80% of these deaths occurred in children who had not received a flu vaccination this season. For the most recent data and more information visit FluView: Influenza-Associated Pediatric Mortality.

Since flu-associated deaths in children became a nationally notifiable condition in 2004, the total number of flu-associated deaths among children during one season has ranged from 37 (during the 2011-2012 season) to 180 (during the 2017-18 season, as of August 11); this excludes the 2009 pandemic, when 358 pediatric deaths from April 15, 2009 through October 2, 2010 were reported to CDC.

How many people were hospitalized from flu during the 2017-2018 season?

From October 1, 2017 through April 28, 2018, 30,453 laboratory-confirmed influenza-related hospitalizations were reported through the Influenza Hospitalization Surveillance Network (FluSurv-NET), which covers approximately 9% of the U.S. population. People 65 years and older accounted for approximately 58% of reported influenza-associated hospitalizations. Overall hospitalization rates (all ages) during 2017-2018 were the highest ever recorded in this surveillance system, breaking the previously recorded high recorded during 2014-2015; a high severity H3N2-predominant season when CDC estimates that hospitalizations captured through FluSurv-NET translated into a total of 710,000 flu hospitalizations that seasons. (For more information on these estimates, see CDC’s Disease Burden of Influenza page.) Estimates on the total number of flu-related hospitalizations during 2017-2018 will be available in fall 2018.

What flu viruses circulated during the 2017-2018 season?

Influenza A(H3N2) viruses predominated overall during the 2017-2018 season. However, influenza B viruses became more commonly reported than influenza A viruses in early March 2018 through May 2018.

How much flu vaccine was produced and distributed during the 2017-2018 season?

Flu vaccine is produced by private manufacturers, so supply depends on manufacturers. For the 2017-2018 season, manufacturers originally projected they would provide between 151 million and 166 million doses of injectable vaccine for the U.S. market. As of February 23, 2018, manufacturers reported having shipped approximately 155.3 million doses of flu vaccine; a record number of flu vaccine doses distributed. More information about flu vaccine supply is available at Seasonal Influenza Vaccine Supply & Distribution.

How effective was the 2017-2018 flu vaccine?

The overall vaccine effectiveness (VE) of the 2017-2018 flu vaccine against both influenza A and B viruses is estimated to be 40%. This means the flu vaccine reduced a person’s overall risk of having to seek medical care at a doctor’s office for flu illness by 40%. Protection by virus type and subtype was: 25% against A(H3N2), 65% against A(H1N1) and 49% against influenza B viruses. These VE estimates were presented to the Advisory Committee on Immunization Practices on June 20, 2018.

While flu vaccine can vary in how well it works, flu vaccination is the best way to prevent flu and its potentially serious complications and prevents millions of flu illnesses and related doctors’ visits and tens of thousands of hospitalizations. For example, during the 2016–2017 influenza season, CDC estimates that flu vaccine prevented an estimated 5.3 million illnesses, 2.6 million medical visits, and 85,000 hospitalizations associated with influenza. Similar estimates for 2017-2018 will be released in fall 2018. Influenza vaccination also has been shown to reduce the risk of flu death in children.