How Long After Second Pfizer Vaccine Is It Effective (And Why)?

Exact Answer: 6 months 

There are numerous COVID-19 vaccines in development around the world. The Food and Drug Administration (FDA) has so far approved three COVID-19 vaccines for emergency use in the United States. The Pfizer vaccine, for example, employs mRNA technology to assist your immune system in developing immunity to SARS-CoV-2, the coronavirus that causes COVID-19. This vaccine is administered in two doses. Your resistance to the virus does not completely kick in until you receive your second dose. You may be curious how long you possess complete immunity after the two doses.

How Long After Second Pfizer Vaccine Is It Effective

How Long After Second Pfizer Vaccine Is It Effective?

The Pfizer vaccine is 91.3 percent effective against symptomatic forms of Covid-19 for up to six months, according to an update of data from clinical trials conducted by Pfizer and its German partner BioNTech. Matter of fact, the two companies announced in a press release on Thursday, April 1, 2021, that the vaccine’s efficacy is being assessed up to six months after the second injection. To obtain these conclusions, the researchers gathered information from over 44,000 patients aged 16 and up, 12,000 of whom were immunized and guided for 6 months after their second dose.

Immune system after the second dose Time 
Low immune (fever might occur)1 week 
Immune system recovers 2 months 
Very high immunity6 months 
  • The Pfizer-BioNTech (COMIRNATY) vaccine was 95 percent helpful in avoiding laboratory-confirmed disease with the virus causes COVID-19 in participants who got two doses and had no evidence of being previously infected, according to findings from clinical trials in people 16 years and older.
  • The Pfizer-BioNTech vaccine was also successful in preventing laboratory-confirmed COVID-19 infection in teenagers 12–15 years old in clinical studies, and the immune response in individuals 12–15 years old was at least as effective as the immune response in people 16–25 years old.
  • In clinical trials, the vaccine was also extremely good at stopping COVID-19 in people of all ages, genders, races, and ethnicities, as well as those with underlying health issues.
  • Evidence suggests that mRNA COVID-19 vaccines provide similar protection in authentic situations as they do in clinical trials, minimizing the chances of COVID-19, including serious infection, by 90 percent or more among completely vaccinated individuals.

Why Is Second Pfizer Vaccine Effective For So Long?

According to the latest research, it takes two doses of the Pfizer-BioNTech COVID-19 vaccine to “wake up” cells that play a key role in the immune system in response, with the second dose increasing their numbers 100-fold. The Stanford University research may help clarify why the second dose of mRNA vaccines, like the Pfizer or Moderna shots, is so important in developing a powerful immune reaction to SARS-CoV-2. The existing pandemic, according to study co-author Bali Pulendran, is “the first time RNA vaccines have ever been given to humans, and we have no idea how they do, what they are doing: offer 95 percent protection against COVID-19.”

Pulendran is a pathology, microbiology, and immunology professor at Stanford. It’s not been clear why mRNA-based flu shots provide such effective coverage against the deadly virus. In contrast, a seasonal influenza vaccine is considered quite efficient if it achieves even 60% security. The Stanford researchers analyzed blood samples from 56 healthy participants at different points during they received their very first second doses of the Pfizer flu shot. The first shot did increase SARS-CoV-2-specific antibody responses, but not well almost as much as the second attempt.       

“The second shot has far more potent beneficial impacts than the first shot,” Pulendran said in a college news release. “It elicited a massive rise in antibody responses, a fantastic T-cell responding that had been missing after the first shot alone, and a remarkably augmented innate immune system.”


In clinical trials and real-world conditions, the Pfizer vaccine for the new coronavirus, SARS-CoV-2, looks to be successful. According to current research, it is safe for the majority of individuals. Chills, fever, fatigue, headache, and soreness or swelling at the injection site are all common adverse effects. This should just be a matter of a few days.               

People can speak with a healthcare expert about various vaccines and their safety. To prevent transmission, people should continue to wear masks, practice physical distance, and follow hygiene requirements until otherwise directed. Millions of people have been infected with the virus, which has resulted in nearly 2 million mortality. Researches have focused around the clock to make useful vaccines, which will be available to the public in December 2020. 


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Hi! I'm Nidhi.

Here at the EHL, it's all about delicious, easy recipes for casual entertaining. So come and join me at the beach, relax and enjoy the food.

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