COVID-19 Vaccine Breakthrough : What You Need To Know!

A vaccine breakthrough infection is what happens when you get infected with COVID-19 even after you are fully vaccinated.

Find out why vaccine breakthrough infections are completely expected, and what we can do to prevent them!


COVID-19 Vaccine Breakthrough : What Is It?

COVID-19 vaccines are like training boot camps for your immune system, giving it an opportunity to learn how to defeat the real SARS-CoV-2 virus.

They greatly protect you from severe disease and prevent death, but even the best COVID-19 vaccine cannot 100% protect you from getting infected.

When someone who is fully vaccinated gets infected by the SARS-CoV-2 virus, this is known as a vaccine breakthrough infection.

The US CDC itself defines a vaccine breakthrough case as a “person who has SARS-CoV-2 RNA or antigen detected on a respiratory specimen collected ≥14 days after completing the primary series of a U.S. Food and Drug Administration (FDA)-authorized COVID-19 vaccine.


COVID-19 Vaccine Breakthrough : Why Does It Happen?

COVID-19 vaccine breakthrough infections are inevitable – partly because no vaccine is perfect, and partly because vaccines rely on the immune system to work.

Do remember – the vaccine does not actually protect you against the COVID-19. It merely mimics the SARS-CoV-2 virus, to help your body learn to fight the real virus.

In some people, the vaccine may not galvanise an adequate immune system response.

In other people, their immune systems may not had sufficient time to produce the necessary antibodies to fight off the infection.

Or they may be infected with a new strain that partly or completely bypasses the training offered by the vaccine.


Vaccine Breakthrough : How To Estimate It?

Now, you might expect the vaccine breakthrough rate to be calculated simply by deducting the efficacy rate from 100%, like so :

  • 95% vaccine efficacy = 5% breakthrough infections
  • 75% vaccine efficacy = 25% breakthrough infections
  • 50% vaccine efficacy = 50% breakthrough infections

However, the vaccine breakthrough infection rate is actually calculated by this formula :

(100% – Vaccine Efficacy %) x Attack Rate

Because the attack rate for COVID-19 is relatively low at about 1%, the real vaccine breakthrough rate is much lower than you would expect.

Breakthrough Rate
Perception Reality
95% 5% 0.05%
85% 15% 0.15%
75% 25% 0.25%
66% 34% 0.34%
50% 50% 0.50%


COVID-19 Vaccine Breakthrough : How To Prevent It?

There are several ways to prevent vaccine breakthrough infections…

Herd Immunity

From a public health perspective, vaccine breakthrough infections are prevented by herd immunity (also known as community immunity).

Even if the vaccine fails to adequately protect some people, transmission of COVID-19 is blocked by other vaccinated people in the community.

This herd immunity provides indirect protection, not just against vaccine breakthrough infections, but also for people who cannot be vaccinated yet – children, people with severe allergies, etc.

However, herd immunity is only achieved when a large majority – most scientists think about 70%-80% – of the population is vaccinated against COVID-19.

Maintain COVID-19 SOP

Until we achieve herd immunity, we must all practice the usual precautionary measures against COVID-19, even if we are fully vaccinated.

Chile is a precautionary tale of what happens if people slack on COVID-19 precautions after getting vaccinated.

Despite vaccinating some 40% of their population, they’re in the throes of a massive surge in COVID-19 cases.

Rapid Vaccination

Even after herd immunity is attained, vaccine breakthrough infections can still occur if the SARS-CoV-2 virus successfully mutates into new variants or strains that partially or completely bypasses the protection offered by current vaccines.

That can happen when there is widespread infection – every COVID-19 infection offers the coronavirus the opportunity to mutate into a different variant / strain.

That is why it is critical to quickly vaccinate everyone. It not only protects us against COVID-19, it also denies the coronavirus the opportunity to mutate.

If we allow the SARS-CoV-2 virus to create new variants or strains that partially or completely bypasses the protection offered by current vaccines, then we have to introduce new vaccines or booster doses that target these new variants.

To avoid this, we must quickly vaccinate everyone across the world.


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