Findings of the CDC’s latest Morbidity and Mortality Weekly Report published Jan. 6, show that severe Covid-19 outcomes or death were rare in vaccinated persons. And, all vaccinated persons who developed severe outcomes had at least one risk factor and most of the vaccinated patients who died had a minimum of four risk factors.

Researchers analyzed the risk factors for severe COVID-19 outcomes among adults who completed a primary vaccination series with a mRNA vaccine (Pfizer-BioNTech or Moderna) or the J&J vaccine ≥14 days before illness onset. Data was sourced from 465 centers in a large US healthcare database. Severe Covid-19 outcomes were defined as hospitalization with a diagnosis of acute respiratory failure, need for noninvasive ventilation (NIV), ICU admission including all persons requiring invasive mechanical ventilation, or death.

Overall, 1,228,664 persons completed their primary vaccination between December 2020 and October 2021. Of these, 2246 developed Covid-19, 327 were admitted to hospital and 189 had a severe disease outcome. Covid-related deaths occurred in 36 patients.

Persons aged ≥65 years and immunosuppressed persons were at high risk of having severe outcomes with adjusted odds ratios (aOR) of 3.22 and 1.91, respectively. Risk for severe outcomes was also higher in persons with at least one of the following six other underlying conditions such as pulmonary disease, liver disease, chronic kidney disease (CKD), neurologic disease, diabetes and heart disease. The aOR of severe outcomes was 1.69 for pulmonary disease, 1.68 for liver disease, 1.61 for CKD, 1.54 for neurologic disease, 1.47 for diabetes and 1.44 for heart disease. 

All fully vaccinated persons who had severe disease had at least one of these risk factors; deaths occurred in those who had 4 or more risk factors. But no such association was observed for sex, race/ethnicity, time since primary vaccination or if the infection occurred during the Delta variant.

The likelihood of having ≥4 risk factors increased in proportion with severity of disease. From nearly 19% in persons with nonsevere outcomes, this increased to almost 57% among patients who had respiratory failure or required intensive care and to ~79% among patients who died.

The aOR for severe outcomes were similar for the Pfizer vaccine and the single dose J&J vaccine at 0.70. However, chances of severe outcomes were lower in those who had taken the Moderna vaccine (aOR, 0.56). Patients who had been infected earlier were less likely to have severe outcomes (aOR 0.27).

This study has identified risk factors that are associated with severe Covid-19 associated outcomes such as ICU admission, respiratory failure or death. It has also shown that severe Covid-19 outcomes or death were rare in vaccinated persons. It reaffirms the beneficial effect of Covid-19 vaccines in reducing the chances of severe Covid-19, including hospitalization and death. This protective effect is further enhanced by booster vaccination.

Even if vaccinated, all at-risk persons must continue to observe all precautions to reduce exposure to Covid-19, take a booster dose (if eligible) along with targeted interventions like chronic disease management, to reduce their risk of severe outcomes.

Reference

1. Yek C, et al. Risk factors for severe COVID-19 outcomes among persons aged ≥18 years who completed a primary COVID-19 vaccination series - 465 Health Care Facilities, United States, December 2020-October 2021. MMWR Morb Mortal Wkly Rep. 2022 Jan 7;71(1):19-25. doi: 10.15585/mmwr.mm7101a4.