Four cases of acquired hemophilia A (AHA) identified after SARS-CoV-2 immunizations in a province in northern Italy caught the attention of researchers, who stressed that the cases are “unusual,” but not necessarily caused by vaccination.
“The overall number of cases observed does not allow … any definitive conclusion over a possible causal relationship between SARS-CoV-2 vaccination and AHA, which would need more epidemiological and pharmacovigilance data about suspected vaccine-related adverse events,” Maria Cristina Leone, MD, of Azienda USL-IRCCS di Reggio Emilia (Italy), and colleagues reported online on Jan. 19, 2022, in a letter to the editors of Thrombosis Research.
The cases, observed in Reggio Emilia during the first 8 months of the vaccination campaign, occurred following receipt of mRNA BNT162b2 (Pfizer-BioNTech) vaccine. The AHA patients included two men and two women who ranged in age from 67 to 86 years.
During this time frame, 235,597 people received at least one dose of BNT162b2 vaccine, the authors noted.
In the 5 years prior, from January 2016 to December 2020, only zero to two cases of AHA were observed each year, totaling five cases, or 1.9 cases per million people/year. These numbers are in line with the estimated incidence of the disease, the researchers noted, adding that “it should nonetheless be underlined that vaccination benefits exceed potential side effects and play a central role in individual and public health to effectively protect people from COVID-19 and stop the pandemic.”
However, they also wrote that the “unusual observation of four cases of a rare disease during the first months of the vaccination campaign in our province could be of interest and could sensitize health care personnel toward a possible complication ofSARS-CoV-2 immunization.”
AHA is a rare autoimmune disease caused by neutralizing autoantibodies against coagulation factor VIII. It is mainly associated with malignancy, autoimmune diseases, certain medications, and postnatal status.
“Sporadic AHA cases have been reported in association with infectious diseases or vaccinations,” the author noted, adding that associations between the BNT162b2 vaccine immune complications, including AHA, have also been reported by other authors.
Three of the four case patients in Reggio Emilia had “at least one common clinical association of AHA,” they found, suggesting that these associations could “reflect susceptibility to autoimmunity potentially triggered by vaccination.”
“Case four died due to complications from sepsis after being treated with steroid and rituximab, whereas the first three cases underwent clinical and laboratory remission after immunosuppressive therapy, and no relapse has been observed during follow-up, as in the other two cases reported: This could suggest a more favorable prognosis in respect to other non–vaccine-associated cases, but longer-term data are definitely needed,” they concluded.
The authors reported having no disclosures.