Introduction
In 2023 a study into batch-dependent safety of the BNT162b2 (Pfizer jab) mRNA COVID-19 vaccine was published. Now in 2024 the study has been repeated with a comparison between Denmark and Sweden. The reason for the repeat study is to see if the new study can scientifically repeat the previous results or not.
Whilst undertaking the original study;
an unexpected batch-dependent safety signal for the BNT162b2 mRNA COVID-19 vaccine was recently identified in a nationwide study from Denmark, but the generalizability of this finding is unknown.
In respect of materials and methods;
[Significant Adverse Events] SAE and vaccine batch data were received from national authorities in Denmark and Sweden, and analyses of heterogeneity in the relationship between numbers of vaccine doses and SAEs per batch were performed, along with comparison of SAE rates and severities for batches that were shared between the two countries.
Results
Significant batch-dependent heterogeneity was found in the number of SAEs per 1000 doses for both countries, with batches associated with high SAE rates detected in the early phase of the vaccination campaign and positive correlations observed between the two countries for the severity of SAEs from vaccine batches that they shared.
Denmark
Denmark and Sweden
Mild SAEs predominated in the batches used in the early part of the vaccination roll-out, where markedly higher SAE rates per 1000 doses in Denmark for the batches that were shared between the two countries suggested that a large proportion of these SAEs were under-reported in Sweden.
Conclusions
The batch-dependent safety signal observed in Denmark, now confirmed in Sweden, suggests early commercial batches of BNT162b2 may have differed from those used later on, and these preliminary and hypothesis-generating results warrant further study.
