In a recent study posted to the medRxiv* preprint server, researchers assessed the efficacy of coronavirus disease 2019 (COVID-19) vaccines in immunocompromised adults.
To date, there have been over 525 million confirmed cases of COVID-19, including more than 6.27 million deaths globally. The immunocompromised population is especially at risk of COVID-19 infection and disease severity. However, extensive research is needed to understand COVID-19 vaccine effectiveness among this population.
About the study
In the present study, researchers compared vaccine effectiveness (VE) of two doses of the messenger ribonucleic acid (mRNA)-based COVID-19 vaccines such as BNT162b2 and mRNA-1273 against breakthrough COVID-19 infections and related hospitalizations among immunocompromised adults.
The team obtained data related to medical and pharmacy claims from 11 December 2020 and 10 January 2022. The data collected included information related to persons insured under Medicare or Medicaid plans, commercial plans, or providers involved in insurance claims submission systems. The team obtained demographic data, including age, gender, and three-digit zip level.
The database also included vaccinations as well as medications dispensed by a pharmacy. The team defined a two-dose vaccination regimen as two doses of the mRNA-1273 vaccine administered to the exposure group or the BNT162b2 vaccine administered to the referent group. At least 14 days duration was maintained between the receipt of two doses of the mRNA1273 or BNT162b2 vaccines. Furthermore, the index date was described as the date when the two-dose vaccine regime was completed.
The study cohort included persons aged 18 years and above who had received two doses of the BNT162b2 or mRNA-1273 vaccine and were monitored continuously via a medical or a pharmacy plan for a year before the index date. The team identified immunocompromised individuals by employing an adapted claims-based algorithm aligned with the official definition of immunocompromised persons eligible to receive COVID-19 booster vaccine doses.
The immunocompromised persons were those who met a minimum of one of the following criteria: (1) stem cell or blood transplant performed two years before the index date; (2) previous organ transplant and immunosuppressive therapy 60 days before the index date; (3) treatment for active cancer 180 days before the index date with a diagnosis for active cancer reported a year before treatment; (4) previous record of immunodeficiency disorder; and (5) previous evidence of human immunodeficiency virus (HIV) infection.
The primary outcome of the study included a breakthrough COVID-19 diagnosis that required medical care, which was defined as a medical claim having the International Classification of Diseases (ICD-10) diagnostic code for COVID-19 in either outpatient, in-patient, emergency, or urgent care. The secondary outcome of the hospitalization related to a breakthrough infection was defined as a hospital stay having the ICD-10 diagnostic code for COVID-19, which was listed as either the primary diagnosis or was reported 21 days before hospitalization.
The team identified 124,879 immunocompromised adults, among which 57,988 persons had received two doses of the mRNA1273 COVID-19 vaccine and 66,981 received two doses of the BNT162b2 COVID-19 vaccine. The study results showed that the overall proportion of breakthrough COVID-19 diagnoses requiring medical intervention was lower in individuals double-dosed with mRNA-1273 than those double-dosed with BNT162b2.
The subgroup analyses showed no differences among the two vaccine cohorts concerning transmission level, date of two-dose vaccine regimen completion, and age. The team also noted that the rate of COVID-19 cases that required medical treatment was lower among the mRNA-1273 vaccines than the BNT162b2 vaccines in the immunocompromised persons having active cancer or primary immunodeficiency. However, no difference was observed among the two vaccine cohorts with respect to COVID-19 medical attention among persons who had a history of blood/stem cell transplant or solid organ transplant.
Furthermore, the team observed that the rate of hospitalizations in breakthrough COVID-19 cases was 3.66 per 1000 person-years (PYs) in individuals vaccinated with two doses of the mRNA-1273 vaccine and 4.68 per 1000 PYs among persons vaccinated with two doses of the BNT162b2 vaccine.
Overall, the study findings showed that the two-dose vaccination regimen of the mRNA-1273 COVID-19 vaccine was more effective among immunocompromised individuals in comparison to the two doses of the BNT162b2 vaccine. The vaccine effectiveness of mRNA-1273 was highlighted in the prevention of breakthrough COVID-19 infections that required medical intervention. The study also indicated that the effectiveness of mRNA-1273 in preventing severe disease outcomes was better than that of BNT162b2 among the immunocompromised population.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.