Study shows difference in antibody levels in response to SARS-CoV-2 infection and type of vaccination

The rapid spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the United States has stretched health care informatics beyond its limits. This is largely due to the increased demand for real-time in-depth information on viral load and antibody responses across the country.

This challenge was further complicated by the lack of accurate and timely testing that was available in the United States at the start of the pandemic. In fact, testing for SARS-CoV-2 was largely performed in response to suspected infections, rather than in a proactive manner. Antibody tests were also rarely performed.

In a recent study published on the preprint server medRxiv,* researchers aimed to monitor the levels of the anti-SARS-CoV-2 spike immunoglobulin G (IgG) levels in populations that were subjected to routine tests. Further, the authors correlated these serum levels with available infection, vaccination, and demographic data.

Study: Comparison of Antibody Levels in Response to SARS-CoV-2 Infection and Vaccination Type in a Midwestern Cohort. Image Credit: vitstudio /

About the study

The current study involved 245 individuals, out of which 135 were female and 110 were male. A total of 19 participants had received the Johnson & Johnson (J&J) single-dose coronavirus disease 2019 (COVID-19) vaccine, whereas 141 and 72 had received the two-dose messenger ribonucleic acid (mRNA) Pfizer and Moderna vaccines, respectively.

Notably, 12 participants had not received any vaccine. A total of 43 participants had a prior infection with COVID-19, with 3 individuals being asymptomatic.

Blood samples were collected from all participants. Titration based on the enzyme-linked immunosorbent assay (ELISA) was performed on the blood samples once a month for a total of eleven months to determine anti-SARS-CoV-2 antibody levels in the blood.

The study involved certain biases such as economic, cohort educational, and racial bias.

Study findings

The results of the current indicate that antibody levels in unvaccinated individuals after infection extended to ten months after infection. Additionally, patient responses to the Pfizer, Moderna, and J&J vaccines were clearly observed ten days post-vaccination. However, more consistent antibody levels were observed twenty days post-vaccination.

Individuals who had received the J&J vaccine exhibited lower antibody levels as compared to the other two vaccines, both in naïve and recovered individuals. Thus, it can be concluded that the efficacy of the J&J vaccine was lower than Pfizer and Moderna vaccines.

Following vaccination with the Pfizer or Moderna vaccines, antibody responses peaked at around 40 days post-vaccination, with levels beginning to decline after 120 days. Further tests will need to be conducted to determine whether the antibody response levels continue to decline or remain at a level similar to recovered individuals. The study also showed that the antibody response for all three vaccines was higher in recovered individuals compared to naïve individuals.

Anti-SARS-CoV-2 spike antibody (IgG) signals from samples from naïve and recovered individuals receiving vaccines from different manufacturers as compared to PCR positive unvaccinated individuals (data replicated from Fig 1). The numbers of independently collected replicates are (from right to left) 46, 122, 331, 8, 40, 31, and 133. Samples collected per individual are shown in Fig. S4.

“We observed little in the way of demographic impacts on antibody production, with only gender impacting infection recovery and no impact of gender, age, or race on responses elicited by the Pfizer and Moderna vaccines.”

Comparison of Female and Male anti-SARS-CoV-2 spike antibody (IgG) signals. N refers to the number of independent replicates. Vaccinated group is only Pfizer and Moderna as other manufacturer groups did not achieve the numbers necessary for statistical comparison.

The study had certain limitations, of which included IgG binding to a single spike isoform, uncertainty in sample collection method and timing, as well as participants belonging only to a local community.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Suchandrima Bhowmik

Written by

Suchandrima Bhowmik

Suchandrima has a Bachelor of Science (B.Sc.) degree in Microbiology and a Master of Science (M.Sc.) degree in Microbiology from the University of Calcutta, India. The study of health and diseases was always very important to her. In addition to Microbiology, she also gained extensive knowledge in Biochemistry, Immunology, Medical Microbiology, Metabolism, and Biotechnology as part of her master's degree.


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  1. Allen Dilliplane Allen Dilliplane United States says:

    Now compare neutralizing antibody levels for NTD, S2, Nucleocapsid, E protein, M protein, nsps, and ORFs.

  2. Jeremaine Prieto Jeremaine Prieto Philippines says:

    What are the expected ranges?

  3. J F J F United States says:

    I'll offer some personal info that may help. I contracted COVID back in Dec 2019 (not labeled then) then in June 2020 I had an antibody test done and it was positive. Earlier this week (9/27/21) I again decided to have another antibody test done. Results: Positive

    I work in a busy south King county (Seattle) hospital emergency room and have since prior to the COVID outbreak. I was not vaccinated at the time of those (2) tests. Nearly 21 months post COVID infection and I still have antibodies. It is wrong to suggest that having antibodies does not mean you're protected. In 21 months of working directly with COVID patients I bet not. It does indeed for many.

    The vaccine while effective isn't always effective for everyone and does not last as long as a naturally occurred antibodies event from COVID infection. Studies are now showing that the so called 'edge' that the vaccine provides to those who've already previously had COVID isn't really an 'edge' at all. Once it wanes your natural immunity affords more than enough. The body stores memory into bone marrow. That is not detectable via traditional antibody test.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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