Rates of ADR Reports by Number of Administered SARS-CoV-2 Vaccination Doses in Sweden: Large Temporal Variations Especially in Consumer Reporting

Introduction: During the SARS-CoV-2 vaccinations in 2021, a record number of Individual Case Safety Reports (ICSR) were submitted to the Swedish Medical Products Agency (MPA). MPA further initiated a record-linkage study [1] by which vaccination data from the National Vaccination Register (NVR) was made accessible. Objective: We aimed at identifying temporal variations in reporting rates of ICSRs by number of administered vaccine doses, and if found, seek plausible explanations to them. Methods: The weekly number of ICSRs submitted to the MPA was divided by the weekly number of administered doses between December 27, 2001, and May 1st, 2022, resulting in the reporting rate per 1,000 doses and week. Results: A total of 102,798 submitted ICSRs and 21.9 million administered doses resulted in an overall reporting rate of 4.7 ICSRs per 1000 doses, range: 0.9/1000 (April 2022) to 21.3/1000 (March 2021). Eighty-two percent of the reports were submitted by consumers. A four-fold increase in reporting rate was observed between weeks 5 and 11, 2021. This coincided with the start of vaccination of prioritized health-care personnel and ensuing mass media activity on e.g. whole hospital wards having to close due to the personnel's flu-like symptoms (fever, headache, fatigue, chills, etc.) following vaccination. On March 16, the Public Health Agency of Sweden decided that only individuals aged 65 or older would receive the Astra Zeneca AZD1222 vaccine. This was followed by a steep seven-fold decline in reporting in three weeks. Reporting rates from both health-care professionals and consumers increased and decreased in a similar fashion. During the summer of 2021, additional peaks in reporting rates were observed. At the same time, menstruation disorders following vaccination were debated in both social and traditional media. The most recent decline in reporting rates, which has yet to turn to an increase, occurred after the Russian invasion of Ukraine in the end of February 2022. The fluctuating reporting rates observed since April 2021 and onwards were almost exclusively seen in consumer reports. Conclusion: Rates of submitted spontaneous reports per 1.000 vaccinations in Sweden varied markedly during the studied period, the most pronounced of which originated from changes in consumer reporting. Many peaks in reporting rates can be-at least temporally-associated to various media or world events, even if a causal relationship can't be proven.