How does a vaccine work? How effective is Pfizer vaccine?


  • There are seven WHO approved vaccines across the world.
  • The Pfizer vaccine shows 95% efficiency after the second dose.
  • The vaccine is recommended for people aged 12 and above.

With lockdowns failing to subside the raging COVID-19 pandemic, vaccines seem to be our only antidote against the deadly virus. Effectiveness of the jabs can be contended, but then the world does not have many options on the table to experiment with: either we lockdown ourselves into our homes, or we vaccinate ourselves.

How does a human body get infected?

When germs – things like bacteria or viruses – attack the human body, they multiply inside it. This invasion of germs, called an infection, is what causes the illness. The immune system uses various tools to fight infection. Blood contains red blood cells, for carrying oxygen to tissues and organs, and white or immune cells, for fighting infection. In some severe cases of infections, you may need external help as well – in form of medicines, injections and hospital care.

What is a vaccine?

A vaccine is a biological formulation that provides artificially acquired immunity to a particular infectious disease. A vaccine usually contains an agent that is a part of or resembles a disease-causing microorganism. The vaccine is made from the weakened or neutralised forms of that micro-organism, its toxins, or one of its surface proteins. These weakened microbes are called as antigens. In short, a vaccine trains the human body’s immune system in a way so that it can fight a disease it has not come into contact with before.

How does a vaccine work? How effective is Pfizer vaccine?

How does a vaccine work?

A vaccine does not cause illness – at least in most of the cases. But what it does is cause the immune system to produce T-lymphocytes (carried in the body by white blood cells) and antibodies. Sometimes, post the vaccination, the imitation infection can cause minor symptoms of the original infection, such as fever. Such minor symptoms are normal and should be expected as the body builds immunity. Once the imitation infection fades, the human body is left with a supply of “memory” T-lymphocytes, as well as B-lymphocytes that will remember how to fight that disease in the future.

How many COVID-19 vaccines have been developed so far?

Since the onset of the global pandemic in March 2020, medical firms and researchers across the globe swung into action and raced against the clock to develop a vaccine. Within a year, multiple vaccines had been formulated. As on date, the World Health Organisation has approved seven COVID-19 vaccines. The approved vaccines include: mRNA-1273 by Moderna, BNT162b2 by Pfizer/BioNTech, Ad26.COV2.S by Johnson & Johnson, AZD1222 by Oxford/AstraZeneca, Covishield (Oxford/AstraZeneca combination) by Serum Institute of India, BBIBP-CorV (Vero Cells) by Sinopharm, and CoronaVac by Sinovac.

How effective is a Pfizer vaccine?

It is one of the most effective vaccines you could find in the market. This vaccine is approved in almost 100 countries across the world. Based on evidence from clinical trials in people 16 years and older, the Pfizer-BioNTech vaccine was 95% effective at preventing laboratory-confirmed infection with the virus that causes COVID-19 in people who received two doses and had no evidence of being previously infected. The vaccine is recommended for people aged 12 and above. However, in case you have had a severe allergic reaction (anaphylaxis) or an immediate allergic reaction (even if it was not severe), to any ingredient present in an mRNA COVID-19 vaccine (such as polyethylene glycol), you should not get either of the mRNA COVID-19 vaccines, according to US Center for Disease Control (CDC).

Bottom Line:

Vaccines are clinically approved after months of rigorous testing. For the greater good of humanity, everyone should get vaccinated against this fast spreading COVID-19 virus.