The effectiveness of this season's flu vaccine was slightly higher in comparison to the flu season of 2017-18, which resulted in 80,000 deaths in the U.S., and the percentage of outpatient visits for flu-like illness was considerably lower.

Flu vaccines were 46% effective against the H1N1 strain of the flu virus and 44% against H3N2 infections, the U.S. Centers for Disease Control and Prevention said in a Feb. 15 report. While the inoculations protected 61% for children between 6 months and 17 years old from the bug, they were only 24% effective for adults 50 and over, the agency added.

A large contributor to the high rates of hospitalizations and illnesses last season was the poor effectiveness of the flu shot. At that time, the CDC reported that the vaccine was only 36% effective overall, with that rate dropping to 25% in protecting people infected by the H3N2 strain.

The flu season — which begins in October, peaks in February and ends as late as May — had a slow start but reached a season-high in late February, according to the CDC's FluView report.

About 5% of outpatient visits during this season were for flu-like illness, whereas last season it went up to almost 7.5% at its peak, according to the CDC. The East Coast and Southeastern states in the U.S. have reported the highest level of flu activity in recent weeks.

The CDC report said it "has been a low-severity flu season, with a lower percentage of outpatient visits for flu-like illness, lower rates of hospitalization and fewer deaths attributed to pneumonia and flu, compared with recent seasons."

Hospitalization rates

According to the CDC, there were 36.6 hospitalizations per 100,000 people, versus 99.9 hospitalizations per 100,000 individuals in the prior season, as of the week ending March 2. There was also a high severity period with the H1N1 and H3 viruses being the predominant strains, whereas last season it was the H3N2 virus strain.

Flu-associated hospitalization rates among children during the current U.S. season have been similar to those observed in other seasons, the agency said. So far this season, there have been 34 flu-related deaths in children, the CDC said.

According to a Morgan Stanley research note from March 4, the flu-like illness rates in the U.S. remain below last season, and the high rates recorded during the 2014-15 season, when 710,000 people were hospitalized in the U.S. More than half of those hospitalized were 65 years or older.

The Morgan Stanley analysts noted that based on doctor visits where patients reported flu-like symptoms, the 2018-19 flu season recorded an average of 2.9% of patients reporting such symptoms between October and February, lower than the 4% average reported during the same period a year ago.

With the peak of the flu season over, the hospitalization rates are declining. The biggest decline in hospitalization rates in comparison to last year occurred in people 65 or older, who are covered by the government's Medicare insurance program, the Morgan Stanley analysts said.

Executive outplacement firm Challenger Gray & Christmas forecast that 20 million workers could take four eight-hour days away from work due to the flu. The firm estimates absences due to illness could cost employers up to $17.59 billion in lost productivity this season. Last year, almost 49 million people, including 32.5 million over the age of 25, got sick, the firm said, citing the CDC's age breakdown of flu infections for the 2017-18 season.

The flu had a negative impact on Community Health Systems Inc.'s emergency room visits in comparison to last season, although overall hospitalization rates remained flat, COO Tim Hingtgen said on the hospital operator's fourth-quarter 2018 earnings call.

HCA Healthcare Inc. reported a negative impact on emergency room visits and facility admissions based on a decline in flu activity from last year, CFO William Rutherford said on a January call. The hospital chain operator noted modest growth for its same-facility admissions and equivalent admissions for the full-year 2018.

US agencies in action

The U.S. Food and Drug Administration, along with its partners across the U.S. Department of Health and Human Services and various pharmaceutical companies, have been working to increase awareness and advance new flu vaccines for the current season.

Apathy seems to be the main reason behind Americans not getting flu shots, according to U.S. Surgeon General Jerome Adams.

Efforts are also being made to update vaccine manufacturing processes. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, has urged more drugmakers to pursue newer techniques, like cell-based and recombinant technologies, which offer faster vaccine manufacturing techniques and can provide more flexibility to rapidly shift to keep pace with changes in the flu virus.

Fauci and his partners are also working on a universal flu vaccine, which could provide robust, long-lasting protection against multiple strains of flu.

Only a few companies have moved to modernize their vaccine manufacturing processes, including GlaxoSmithKline PLC; CSL Ltd. unit Seqirus Inc., which produces a cell-based product called Flucelvax; and Sanofi unit Protein Sciences Corp., which makes a recombinant protein-based vaccine Flublok.

Vaccine sales

Several large drugmakers with significant vaccine portfolios reported an increase in sales of their flu vaccines during the fourth quarter, including Sanofi, which recently got expanded U.S. approval for use of its Fluzone Quadrivalent in young children and will be available for the 2019-20 flu season.

CSL, whose Seqirus unit manufactures flu vaccines including Afluria, Fluad, Flucelvax and Fluvirin, cited strong growth in its flu vaccines business on its most recent earnings call.

GSK's sales for 2018 were up 16%, driven partially by a 10% bump in flu vaccine sales, CFO Simon Dingemans said on the fourth-quarter earnings call.

Meanwhile, Roche Holding AG is looking to commercialize Xofluza after it became the first new antiviral flu treatment to be approved by the FDA in nearly 20 years. The Swiss drugmaker, which is collaborating with the U.S. government to combat flu and other health risks, also is seeking FDA approval for Xofluza to treat people at high risk of complications from flu.