Infectious disease expert weighs in on new flu drug

Dr. Spencer Durham of Auburn University’s Harrison School of Pharmacy offers insight below into the new flu drug, Xofluza. He is a board certified pharmacotherapy specialist and has a qualification in infectious diseases from the Board of Pharmacy Specialties. Dunham is an assistant clinical professor.

1. The FDA has approved a new antiviral influenza treatment called Xofluza (baloxavir marboxil). How does this differ from other antiviral treatments, like Tamiflu, and what should people know about it?
   
   Xofluza is the first new antiviral treatment for the flu that the FDA has approved in almost 20 years. It is given as a one-time dose by mouth and is recommended for patients 12 years of age and older who have had symptoms of the flu for less than 48 hours. Xofluza works in a different way than other antivirals, such as Tamiflu (oseltamivir), by inhibiting an enzyme called polymerase acidic endonuclease, which is required for the flu virus to replicate. In clinical trials, Xofluza worked as well as Tamiflu in helping symptoms of the flu, and had fewer adverse effects. In addition, Xofluza has the advantage that it can be used for the treatment of flu strains that have become resistant to drugs like Tamiflu. Another potential advantage of Xofluza is that it requires only a one-time dose, whereas Tamiflu must be given twice a day for 5 days.

2. As we are in flu season, how do the different strains of the flu affect the vaccine?
   
   There are many different influenza strains that circulate each year, which are broadly classified as influenza A viruses and influenza B viruses. Scientists review these strains each year to try to predict which ones they believe will be most prevalent, and these strains are included in the annual vaccine. While these predictions are usually very accurate, sometimes there are strains not included in the vaccine that become prevalent. The flu vaccine generally contains two strains of the influenza A virus and one strain of the influenza B virus (trivalent vaccines). Some vaccines contain an additional strain of the influenza B virus (quadrivalent vaccines).

3. When should people get vaccinated for the flu?
   
   Influenza season generally begins in October and can last through May, with peak activity usually between December and February. Patients should get vaccinated as soon as possible after the vaccine is available, and ideally prior to peak activity. The CDC recommends that vaccination occur prior to the end of October of each year. However, even if it is late in the season, vaccination is still beneficial and is recommended.

4. The flu vaccine last year didn’t seem to be very effective. What was the reason for that?
   
   It is true that the flu vaccine last year was not as effective as it had been in past years. The CDC estimates that the overall effectiveness was around 40%, whereas the overall effectiveness in past years has been around 60%. Last year, the H3N2 strain, which is a type of influenza A virus, was the predominate circulating strain. This particular strain is usually more severe than other strains, and the vaccine is not as effective for it. This is largely why the flu season last year was worse than in previous years, and why the vaccine did not seem to work as well.
   
   For the current season, the H3N2 strain included in the vaccine has been updated to better match the circulating strain, which will hopefully result in better protection against this strain compared to last year. It is important to remember that, even if a patient gets the flu after receiving the vaccine, it is not usually as severe as if the patient had not received the vaccine at all. This is one of the reasons it is so important to get vaccinated.

5. While it is still early, how effective has the 2018 flu shot been?
   
   The CDC reviews the effectiveness of the vaccine each year. However, because it is still so early in this season, we don’t know yet how effective the current vaccine has been in North America. However, influenza season in the southern hemisphere of the world, such as in Australia, begins prior to the season in North America, and the current vaccine appears to have worked well in the southern hemisphere, and better than last year’s vaccine.

6. Are there certain populations that may be at higher risk during this flu season?
   
   Certain patients are at a higher risk of developing complications from the flu, such as pneumonia or having to be hospitalized. These patients include: children age 6 months to 5 years; adults 50 years of age and above; patients with chronic lung diseases, such as asthma and COPD; patients with diabetes mellitus; and patients who have lower immune system function, such as patients who have cancer or HIV.
   
   It is important to keep in mind that it is recommended for all patients to receive the flu vaccine, not just these patients who are at higher risk of complications.

7. Is it true that the vaccine can give someone the flu?
   
   No, the flu vaccine cannot give a person the flu. The injectable form of the vaccine uses viral strains that have been inactivated, or killed, and therefore cannot cause the flu. Sometimes, patients may experience very mild muscle pains, headache, or low-grade fever after receiving the vaccine. Because these symptoms are similar to symptoms of the flu, some patients may mistakenly believe they have been infected with the flu. However, true influenza infection usually causes moderate to severe symptoms and lasts for several days or even a week, whereas the symptoms after receiving the vaccine are very mild and last only 1-2 days.
   
   Unlike the flu shot, the nasal flu vaccine uses a live virus. However, this virus has been so severely weakened that it is not capable of causing the flu.