Case study describes consequences of undetected SARS-CoV-2 infection during mRNA vaccination

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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen behind the coronavirus disease (COVID-19) pandemic, continues to spread globally. To date, over 158.9 million cases and over 3.3 million deaths have been reported.

Nearly a year after the pandemic emerged in December 2019, vaccine roll-outs have now commenced in most countries.

Now, a new report describes a case of a coincidental mRNA vaccination and SARS-CoV-2 infection in a 31-year-old doctor, addressing the theoretical considerations for potential risks and further required actions in case more cases appear in the future.

Published in the journal Infection, the study highlights the need for rapid testing for an additional possible SARS-CoV-2 infection in case of alleged vaccine reactions lasting longer than one day.

SARS-CoV-2 vaccination

Since December 2020, many countries have started vaccinating their populations, prioritizing healthcare and frontline workers. From there, vaccination campaigns ramped up in many parts of the world to inoculate as many people as possible in an attempt to attain herd immunity.

One of the newest technologies used in the production of vaccines is the mRNA platform. These vaccines protect against infectious diseases by teaching host cells to make a protein or a piece of a protein that induces an immune response. To produce an mRNA vaccine, scientists make a synthetic version of the mRNA that the virus uses to develop its infectious proteins with host cell machinery.

The immune response to SARS-CoV-2 infection remains unclear, but so far, scientists know that the median time to seroconversion for both immunoglobulin G (IgG) and the immunoglobulin M (IgM) antibodies is about two weeks from symptom onset. However, antibody responses do not always develop along the same course for everyone and can depend on the severity of the disease.

Case study

In the case study, the researchers described a male physician-patient who developed symptomatic COVID-19 coincidentally shortly after receiving his first vaccine dose.

The 31-year-old male physician was working in a non-specialized non-intensive care COVID-19 unit when he developed flu-like symptoms a few hours after receiving his first Pfizer-BioNTech COVID-19 vaccine shot.

The doctor reported symptoms including headache, coughing, chills, fever, and generalized limb pain. When the symptoms did not improve during the following day, the doctor underwent nasopharyngeal swab testing to determine if he was infected with SARS-CoV-2. The patient tested positive, but due to the lack of respiratory symptoms, he was advised to undergo home isolation.

Since the patient used the mRNA vaccine for the first time with flu-like symptoms and highly positive SARS-CoV-2 copies in the nasopharyngeal swab, clinicians asked certain questions about the case. They wanted to know whether the doctor’s symptoms were caused by the vaccine’s side effects or the SARS-CoV-2 infection itself. They also wanted to determine whether mRNA vaccines can affect the accuracy of polymerase chain reaction (PCR) tests and if vaccination on top of a current SARS-CoV-2 infection poses any health risks.

To address these, the researchers tested the patient for SARS-CoV-2 antibody responses using commercially available serological assays. They also obtained a nasopharyngeal swab, containing 1.7 million copies/ml, down from the 32 million copies/ml during the first test.

When the team repeated the same procedure after ten days, the viral load further decreased to 0.013 million copies/ml. A seroconversion also took place for the nucleocapsid (N) IgG and spike (S) protein IgG antibodies; there was also a seroconversion of IgG but not IgM antibodies.


The researchers concluded that the possibility of coincidental infection with SARS-CoV-2 and vaccination is high in people who are highly exposed to the virus, such as healthcare workers.

Further, patients should not be worried about the PCR test showing a false positive through vaccination. It is highly unlikely that the mRNA vaccination, which is injected into the deltoid muscle, would be detected in the nasopharyngeal area.

The team also noted that the vaccine appeared to be well-tolerated despite the doctor having an existing SARS-CoV-2 infection. When the team tested for the levels of interleukin-6, c-creative protein (CRP), procalcitonin, leukocytes, and kidney or liver values, the results did not show any pathological lab results seven days after the onset of symptoms.

In a nutshell, the researchers recommend that there is no need for SARS-CoV-2 testing before receiving the vaccine, since simultaneous infection and vaccination do not seem to increase the risk for a more severe disease course.

The team also recommended rapid testing for an additional possible SARS-CoV-2 infection in cases of alleged vaccination reactions that last longer than one day.

Journal reference:
Angela Betsaida B. Laguipo

Written by

Angela Betsaida B. Laguipo

Angela is a nurse by profession and a writer by heart. She graduated with honors (Cum Laude) for her Bachelor of Nursing degree at the University of Baguio, Philippines. She is currently completing her Master's Degree where she specialized in Maternal and Child Nursing and worked as a clinical instructor and educator in the School of Nursing at the University of Baguio.


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