What is influenza?

Influenza, more commonly referred to as flu, is a respiratory disease caused by the influenza virus that infects the nose, throat and often the lungs. It is a highly contagious disease that can be mild or severe with complications, arising particularly, in the very young, very old and in those with certain medical conditions. Every year in the winters, this virus causes epidemics in communities everywhere and is the cause of hundreds of thousands of hospitalizations and thousands of deaths. As flu season comes near in the United States, health experts have warned that the flu epidemic this year may be particularly burdensome because of the ongoing COVID-19 pandemic.


During a particularly bad flu season, which culminates from December to February, about 40 to 50 million Americans may be infected with influenza and some 800,000 may require hospitalization according to Charles Chiu, MD, PhD, an infectious disease expert at UC San Francisco.

What are the symptoms of Influenza?

Influenza or flu is different from the common cold. The symptoms for flu usually start suddenly and the people infected may experience some or all of these symptoms:

  • Dry, persistent cough
  • Sore throat
  • Runny or stuffy nose
  • Fever may be with chills and sweats
  • Muscle ache
  • Headaches
  • Fatigue
  • Vomiting and diarrhoea, more common in children

The flu virus is spread mainly through tiny droplets of secretions from infected people when they cough, sneeze or talk and can infect other people close by. Less commonly a person can also get infected by touching surfaces or objects that have been recently touched by a patient, and have the virus on it, and then touching their face, nose or eyes.

Why is vaccination important?

The best prevention against influenza virus, although not 100% effective, is getting an influenza vaccine yearly. Annual flu vaccination is recommended by the Centre of Disease Control and Prevention (CDC) for everyone aged 6 months or older. The flu vaccine has proven to have many benefits such as reducing the risk of getting the flu, hospitalization, and also the risk of flu-related deaths in children.

Should I get a vaccine every year?

The flu vaccine is recommended yearly because the flu viruses evolve so quickly, last year’s vaccine might not be protective against the newly evolved virus. Thus, new flu vaccines are developed every year to keep up with the evolving virus. After getting vaccinated it takes about 2 weeks until full immunity develops but the flu vaccine is beneficial even if one gets it after the flu season has started. It is recommended for people in the US to get vaccinated against influenza in September and October. However, one can also protect themselves against late outbreaks of influenza if they get vaccinated in February or later.

How does the vaccine work?

The vaccine works by causing protective antibodies to develop in the body against the influenza virus which is included in the vaccine. However, the antibody levels may decrease over time which is another reason why we need to get vaccinated yearly.

Majority of the flu vaccines in the US protect against 4 different strains of flu viruses. Some vaccines that protect against 3 different types of viruses are also available. The effectiveness of the flu vaccine varies for different people. For example, the flu vaccine has proven to be more effective for people younger than 65 years, it may not be as effective for older people with certain medical conditions and the studies have shown that that the vaccine is 50%-60% more effective for healthy adults between 18 to 64 years of age.

Even though the vaccine is not 100% effective and does not completely prevent the flu, it can lessen the severity of the disease and also reduces the risk of developing complications and needing hospitalization.

Why get vaccinated in COVID-19 era?

It is especially necessary to receive the flu vaccine this year, as the flu and coronavirus present with similar symptoms. The vaccine does not protect against coronavirus but it can reduce similar symptoms of the flu that can be confused with COVID-19. Prevention against the flu and its serious complications also reduces the number of people requiring hospitalizations thereby relieving the hospitals already burdened by COVID-19.

Is it safe?

The flu vaccine is very safe to use, however, some people should not get it or should talk to their doctor before getting one. They include; infants less than 6 months old, people who have previously had a severe allergic reaction to the flu vaccine, people with egg allergy and individuals with Guillain-Barré syndrome. Thus, it is important to get the flu vaccine as it will not only protect us but also protect those individuals who can not receive the vaccine. This is the concept of herd immunity and it is very important in eliminating diseases.

For those who are afraid of needles, a nasal spray vaccine is also available and approved for use in healthy, non-pregnant individuals, 2 years to 49 years of age.