COVID-19 Reinfection Post Vaccination – Demystifying Rumors

COVID-19 Reinfection Post Vaccination – Demystifying Rumors

Vaccines are not 100% effective, in no small part due to mutation. Covid-19 reinfection that occur after vaccination are called “vaccine break through cases”. The real-world data after 100 million vaccinations is identical to the results of phase 3 clinical trials.

Covid-19 Reinfection

Trials of messenger RNA (mRNA) vaccines through November 2020 showed about 95% efficacy for the prevention of symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection at 14 days after the second dose of the mRNA vaccinations with slight superiority of Pfizer over Moderna. Since the results of these trials were published, Food and Drug Administration has granted emergency use authorization for these two mRNA vaccines, and vaccination has been initiated across the United States. More than 150 million people in the United States have been fully vaccinated as of June 21, 2021.

This article aims to demystify the efficacy of FDA approved vaccinations, Covid-19 reinfection rates post vaccination and protection from variants of the virus.

Viruses constantly change through mutation, and new variants of a virus are expected to occur. Sometimes new variants emerge and disappear, or they may persist. Multiple variants of the virus that causes COVID-19 have been documented in the United States and globally during this pandemic.

Vaccines for viral infectious process are not 100% effective, in no small part due to mutation. Cases of Covid-19 that occur after vaccination are called “vaccine break through cases”. Several months after initiation of vaccination programs and more than 100 million people vaccinated, we have real-world experience and data. The data is identical to the results of phase 3 clinical trials in reported November 2020. Therefore, there will be cases of Covid-19 reinfection even after vaccination.

Definition of Vaccine breakthrough infection is – the detection of SARS-CoV-2 RNA or antigen in a respiratory specimen collected from a person ≥14 days after they have completed all recommended doses of a U.S. Food and Drug Administration (FDA)-authorized COVID-19 vaccine.

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There are six Covid-19 variants in the US –

  • B.1.1.7 (Alpha): Initially detected in the UK. First detected in the United States in December 2020.
  • B.1.351 (Beta) or the South African variant: Initially detected in South Africa in December 2020. This variant was first detected in the United States at the end of January 2021.
  • P.1 (Gamma) or the Brazil variant: First detected in the United States in January 2021. P.1 was initially identified in travelers from Brazil, who were tested during routine screening at an airport in Japan, in early January.
  • B.1.427 and B.1.429 (Epsilon): These two variants were first identified in California in February 2021.
  • B.1.617.2 (Delta): Initially identified in India during the massive breakout in December 2020. It was first detected in the United States in March 2021.

Thus far, studies suggest that the current authorized vaccines work on the circulating variants.

Also Read: COVID-19 and Brain Damage – What We Know So Far

The range of sickness post vaccination may vary from the most common asymptomatic infection to very rare hospitalization and death.

The common causes of break through infections are: – infection prior to attaining complete protection from the vaccination or being infected prior to the vaccination. It takes approximately 2 weeks to get optimal protection after vaccination. Although the vaccines approved in the US provide protection against most variants, some variants of Covid-19 viruses may cause infection and clinical symptoms.

CDC is looking into reasons for breakthrough infections to identify unusual patterns like age, gender, vaccine difference and variants. So far there are no unusual patterns that have been identified. A total of 10,262 SARS-CoV-2 vaccine breakthrough infections had been reported from 46 U.S. states and territories as of April 30, 2021. At that point about 101 million people had been vaccinated in the United States. Among the Covid-19 reinfection cases, 6,446 (63%) occurred in females, and the median patient age was 58 years (interquartile range = 40–74 years). Based on preliminary data, 2,725 (27%) vaccine breakthrough infections were asymptomatic, 995 (10%) patients were known to be hospitalized, and 160 (2%) patients died (Ref 1).

In conclusion, FDA approved SARS-CoV-2 vaccines are effective. After vaccination it is prudent to continue following hygiene protocol i.e. personal space of about 6 feet, avoiding crowded places without adequate air circulation and hand hygiene. AS CDC guidelines evolve, it is pertinent to keep up with and follow them.


  1. COVID-19 Vaccine Breakthrough Infections Reported to CDC — United States, January 1–April 30, 2021. MMWR Morb Mortal Wkly Rep 2021;70:792–793. DOI: