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How Effective Is A Flu Shot?

12/12/2020 | by

Influenza, an acute, highly contagious respiratory disease caused by a variety of different but related viruses, has been a literal plague on humanity for centuries. Records of an upper respiratory disease with symptoms consistent with influenza date as far back as 412 BC with Hippocrates’ writings of the “cough of Perinthus”. For most of the time since, society has been poorly equipped to deal with the disease in any substantial way. That is, until 1936 when the first antibodies for influenza were isolated, which would later provide the basis for subsequent vaccines against influenza.

Luckily, in the current era, we have access to the yields of modern medicine, and with them the flu vaccine. Despite this, you may have heard that the flu vaccine is not 100% effective. To understand why this is, it’s helpful to first have an understanding of how the flu vaccine is manufactured.

How the flu vaccine is created

In common speech, “seasonal flu” is something with which we are all too familiar. How the flu vaccine is fabricated, on the other hand, is less well known. The process of creating an effective vaccine against seasonal flu is complicated and ongoing.

Influenza is subject to a process called antigenic drift: mutations within the genes of the virus that cause changes to the structures to which the immune system responds. These structures, called antigens, are what the immune system recognizes after it has had exposure to the virus. This recognition will begin the production of antibodies that block infection. Antigenic drift happens on an ongoing basis as the virus replicates over time.

Vaccines, including the influenza vaccine, generally involve exposure to an innocuous form of the disease to enable antibody production within the patient, preempting the body’s immune response system before true exposure. Antigenic drift becomes an issue when the mutated form of the virus changes such that it no longer resembles the disease against which a patient was inoculated. The body’s immune system is no longer able to recognize the virus and avoid infection. The antibodies created by the vaccine are unable to recognize the mutated form of the disease.

Why do you need to get the flu shot every year?

The Center for Disease Control is tasked with predicting the degree to which influenza will antigenically drift between flu seasons. This is why it is recommended that one get their flu shot annually as opposed to other vaccines which require less upkeep. This is also why a flu shot is not an absolute guarantee that one will not contract a flu infection: sometimes the degree to which a virus has drifted is such that the flu vaccine is not a great match.

In large part, because there is so much variability to the genetic structures of the influenza virus, thanks to antigenic drift, the CDC must closely monitor just how effective vaccines are. They use several different networks to monitor hospitalizations related to respiratory illness. Upon testing for flu, the frequency of influenza vaccination among patients is observed as compared with non-vaccinated patients.

How effective will the flu shot be in 2022?

As we have seen, it is not known with complete certainty how effective a flu shot will be for the current season; the extent of antigenic drift can vary greatly and information related to efficacy will not be available until after the end of the season. With that said, the composition of the flu vaccine for the 2021 – 2022 season has been updated and will offer protection against four influenza viruses.

Even antigenically drifted viruses share genetic similarities with their original variants, so there is still a protective benefit from the flu shot. Even in the worst-case scenario of infection despite having been vaccinated, the flu vaccine has been shown to reduce the severity of symptoms. This, in turn, minimizes the chance of developing complications or requiring hospitalization.

The flu shot is the best way to prevent infection and is strongly recommended, especially during the pandemic when hospitals are over-burdened with Covid-19 cases.

How effective were flu shots in the past?

Each year, the CDC plays this game of cat and mouse with influenza; they are charged with predicting the genetic makeup of the viruses that will constitute the upcoming seasonal flu. Some years are more successful than others. Over the 2019-2020 flu season, for example, the flu shot was 29% effective. In the previous season, that number was about 38%. In the 2015-2016 season, the flu shot was 48% effective.

Data for the effectiveness of the 2020 – 2021 vaccine are not available. However, the flu season for that year was very quiet, largely attributed to Covid-19 and the concomitant social distancing, mask wearing, and sanitization protocols.

How long does a flu shot last?

The flu shot is annual for a reason: as we have read, influenza possesses certain properties which make it impossible to vaccinate against in perpetuity. So, when we ask for how long a flu shot will last, the answer can change according to the genetic makeup of the particular flu strain which appears over the season.

As a rule, though, the flu shot will provide immunity for 4 – 6 months after vaccination. Getting a flu shot every year during September or October will ensure that you are as prepared as possible for the course of flu season.

Are flu shots effective for people over 50 and seniors?

It is advised that seniors get their annual flu vaccination. Analysis of the effectiveness of flu vaccine among seniors aged 60 and over demonstrate efficacy percentages at 52% in years when the seasonal flu strain was well predicted; effectiveness was closer to 36% when the vaccine was not well matched to the predominant flu strain.

Are flu shots effective for toddlers and young children?

The CDC also advises that children get their flu shot. In a four-year study which looked at the efficacy of the flu vaccine among children aged 1 to 15, rates of successful vaccination were 77% and higher for a particular, common strain of the seasonal flu.

At-Home Flu Shots With Drip Hydration

If you want to get a seasonal flu shot but don’t want to risk exposure to Covid-19 at a clinic or pharmacy, Drip Hydration can help. We bring your flu shot directly to you in the comfort of your own home. Avoid unnecessary exposure to Covid-19 and the inconvenience of leaving your residence and book an appointment with one of our registered nurses today.

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