The flu vaccine comes in two forms: As a regular shot and a nasal spray, which is great for kids and those squeamish about needles. The following information will answer the common questions people have about the flu vaccine.

Who needs a flu shot?

Pretty much everyone, adults and children alike. In 2008 the CDC changed its recommendations to suggest that all healthy kids ages 6 months to 18 years get the flu shot. (Babies under 6 months can’t get the flu shot.) Before it was listed as optional. The policy change came as a way to try and curb flu deaths among otherwise healthy children. So unless someone has a compromised immune system or other specific medical condition that prevents them from being immunized, everyone in your family should get a flu shot. The CDC advises that at least 70% of Americans get flu shots each year to help reduce its spread.

Does the flu shot cause the flu?
No. It’s impossible for the shot to give you the flu, since the viruses in the vaccination are dead. Although the nasal spray contains weakened live viruses, they are not powerful enough to cause severe symptoms.

What’s in a flu shot?
Flu shots typically include 4 strains of flu virus: two A strains and two B strains. B viruses are those that typically affect only humans, whereas A viruses can infect both people and animals, giving them a greater ability to mutate and spread. The particular strains included are chosen by the World Health Organization each year, based on their best estimates of which strains are likely to be a problem. The annual flu vaccine now includes protection against HINI.

Vaccines also include preservatives and other inert material, but there is no thimersol or methyl mercury. So there is no reason to worry about vaccines causing autism.

Why do I have to get a flu shot every year?

Because the influenza virus is constantly changing and evolving, getting a flu vaccine one year doesn’t offer protection against the strains of flu that are in circulation the next year. Before each flu season, health organizations carefully assess what strains they expect to circulate and include those in the vaccination. When the structure of a flu virus mutates, the vaccine won’t be effective, since all a vaccine does is introduce an intruder to your immune system so that it can learn to recognize and defeat it and have antibodies at the ready.

With so many strains of the flu and so many possible ways it can mutate, health officials can’t stockpile vaccines, and by the time the new flu season rolls around, the last season’s strains are typically long gone. Researchers are hard at work trying to identify ways to target the different strains together to produce a universal flu shot, but so far these efforts have come up empty.

How effective are flu vaccines?
Flu vaccines are typically 60% to 90% effective, but this can fluctuate wildly depending on the particular strains going around that year and how accurately health officials have forecast them. During the 2007-08 flu season, for example, the vaccine was only 44% effective. The 2014-15 season saw a vaccine that was only 19% effective, and the following two years it averaged 40% effective. (McGinty, 1-5-2019)

However, “Even if you get the flu after having had the vaccine,” says Dr. William Schaffner, an infectious disease specialist, “you are substantially protected against the complications, pneumonia or death.” (McGinty, 2019) So even if it doesn’t work perfectly to keep you flu-free that year, there are benefits to getting vaccinated.

Which works better: Flu shot or nasal spray?
Studies show that the nasal-spray vaccines are actually more effective than shots at preventing the flu in children (probably because they contain a live but weakened virus that prompts a more robust immune response). However, the mist is not recommended for children under age 2 or those with conditions such as asthma or heart disease.

Isn’t it better just to let my kid get sick and build a natural immunity?
According to a survey by Consumer Reports, 69% of parents say they’d prefer their children get sick and build a “natural immunity” rather than getting vaccinated. (Weise, 10-21-2009) Though it is true that natural immunity lasts longer than that which comes from a vaccination, it’s also more dangerous. Remember that flu is a virus that can sometimes kill perfectly healthy children. Put things in perspective, flu will kill more healthy children this year than will be murdered by registered sex offenders in the next 200 years. Yet parents who would never let their child play near the home of such an individual think nothing about forgoing a flu shot and putting their child at much greater risk.

The flu vaccine can also have a cumulative effect when you take it year after year, since each vaccine targets different strains. Nor is it perfect, which means that if your child gets the vaccine and it works, they’ll have immunity, and if it doesn’t, then they’ll have a chance to work on building that natural immunity (usually with milder symptoms). But the safest thing to do in order to give them the most protection is to get them vaccinated.

How long does it take for the flu shot to work?
It can take up to a couple of weeks after getting the shot for the vaccine to take effect. Within that period, you could still come down with the flu.