In the phase 3 clinical trials (P301) for the Moderna COVID-19 vaccine (mRNA-1273), 22.2% of the sample population had high-risk underlying diseases [4]. The most common comorbidities were DM (9.4%), severe obesity with body mass index (BMI)≥ 40 kg/m2 (6.5%), severe heart disease (4.9%), and chronic lung disease (4.8%). Patients infected with human immunodeficiency virus (HIV; 0.6%) were also included. On analyzing the preventive effect according to the presence of comorbidities, similar preventive effects were observed in the group without comorbidities (94.0%; 95% CI, 83.5 to 97.8) and the group with comorbidities (95.9%; 95% CI, 69.7 to 99.4). Participants with severe obesity, one of the most common comorbidities, showed a preventive effect of 91.2%(95% CI, 32.0 to 98.9). In the vaccinated participants with DM, severe heart disease, chronic lung disease, and HIV infection, statistical significance was not demonstrated since the lower limit of 95% CI was unable to be assessed, although no symptomatic COVID-19 infection was detected in the vaccination group. The frequency of adverse events were similar in the group with comorbidities and the total sample population. Thirteen deaths were reported: six in the vaccination group and seven in the control group. Of the deaths in the vaccination group, three patients had underlying heart disease, one had hypertension, and one had Crohn’s disease with short bowel syndrome. It was assessed that the deaths were not associated with the vaccine.

In the phase 2 and 3 clinical trials (AZD1222) performed in the UK and Brazil for the AstraZeneca COVID-19 vaccine (BNT162b2), 39.3% of the sample population had one or more underlying diseases, including obesity with BMI≥ 30 kg/m2, cardiovascular disease, lung disease, and DM [5]. The phase 2 and 3 clinical trials (COV002) performed in the UK included patients with cardiovascular disease (11.5%), lung disease (12.4%), and DM (2.2%). The phase 3 clinical trials (COV003) performed in Brazil included patients with cardiovascular disease (15.6%), lung disease (10.0%), and DM (3.8%). Although the preventive effect was slightly lower in patients with one or more underlying diseases (58.3%; 95% CI, 33.6 to 73.9) than in the total sample population, the difference was not statistically significant. Among the patients, four (one in the patient group and three in the control group) died due to causes other than COVID-19, including traffic accident, trauma, murder, and pneumonia. It was concluded that the deaths were not associated with the vaccine [6].