Breakthrough Severe COVID-19 Infection After Triple Dose Pfizer Vaccination

The impact of COVID-19 was felt across the globe when it first emerged in December 2019. However, within a year, there was a new hope with the development and approval of mRNA vaccines. The Comirnaty and Pfizer-BioNTech BNT162b2 mRNA vaccine showed an efficacy of 95 percent in preventing COVID-19 disease. However, subsequent studies conducted on immunocompromised hosts showed the efficacy to be significantly lower than the initial reported 95 percent, making these patients prone to COVID-19 disease despite the initially recommended two doses. On Sept. 22, 2021, a third dose was approved for immunocompromised hosts. In this article, we report the case of a 67-year-old female with overlap connective tissue disease on mycophenolate mofetil who had a prolonged hospital course because of severe COVID-19 disease complicated by pulmonary embolism despite receiving three doses of the BNT162b2 mRNA vaccine.