Analysis · Health
Why an Antibody Gap Is Not a Measure of the Hospitalization Gap
By AWEI · AI-compiled · Published · Analysis prepared · 1 source · doi.org
A striking gap in antibody levels did not translate into an equally dramatic gap in estimated protection against hospitalization. In a 2021 vaccine comparison, Janssen recipients had much lower measured antibody levels than Moderna or Pfizer-BioNTech recipients. Yet Janssen’s estimated effectiveness against COVID-19 hospitalization was still 71%. The two measurements answered different questions.
Wesley H. Self and colleagues in the IVY Network studied 3,689 adults hospitalized at 21 U.S. hospitals during March–August 2021, excluding people with immunocompromising conditions. They compared vaccination histories between COVID-19 cases and hospitalized controls who tested negative. After adjusting for admission date, region and demographic factors, estimated effectiveness was 93% for Moderna, 88% for Pfizer-BioNTech and 71% for Janssen.
The antibody evidence came from a separate group: 100 healthy volunteers sampled once, two to six weeks after completing vaccination. Median antibody levels against the virus’s receptor-binding domain were 4,333 units per milliliter for Moderna, 3,217 for Pfizer-BioNTech and 57 for Janssen. These were measurements of binding antibodies, not direct measurements of protection.
Crucially, the researchers did not follow these volunteers to connect their individual antibody results with later hospitalizations. Placing the two analyses alongside each other therefore could not establish how much protection a particular antibody level conferred, or prove that antibody differences caused the hospitalization differences. Cellular immune responses and changes in antibodies over time were not measured.
The hospital comparison also had limits. Vaccination was not randomly assigned, so unmeasured differences between groups could affect the estimates. Only 113 hospital participants had received Janssen; its effectiveness estimate had a wide 95% confidence interval, from 56% to 81%. Effectiveness was not estimated separately by variant.
The useful lesson is to check whether laboratory measurements and clinical outcomes were linked in the same people. Here, the antibody findings supplied biological context, but no conversion rule from an antibody result to someone’s likelihood of hospitalization.
Sources used for this article (1)
Direct links to the publisher reports used to prepare this article.
- Source 1
- Comparative Effectiveness of Moderna, Pfizer-BioNTech, and Janssen (Johnson & Johnson) Vaccines in Preventing COVID-19 Hospitalizations Among Adults Without Immunocompromising Conditions — United States, March–August 2021 ['Wesley H. Self', 'Mark W. Tenforde', 'Jillian P. Rhoads', 'Manjusha Gaglani', 'Adit A. Ginde', 'David J. Douin', 'Samantha M. Olson', 'H. Keipp Talbot', 'Jonathan D. Casey', 'Nicholas M. Mohr', 'Ann
