Aim: To investigate the reasons for rehospitalization among patients recovered from COVID-associated pneumonia.

Material and methods: 35 patients (pts) survived severe or critical COVID-associated pneumonia were observed during 6 months. 10 (29 %) pts experienced rehospitalization during follow-up period whereas 25 (71%) pts did not. Non-parametrical statistical methods were used.

Results: Median day of rehospitalization was 60 (45; 70) from the beginning of COVID-19. Reasons for rehospitalization were the following:

1. Pulmonary embolism (PE) happened in 3 (30%) pts at 35 (35; 47,5) day from the beginning of COVID-19. In 2 cases PE was associated with anticoagulation withdrawal whereas in 1 case PE happened during anticoagulation and led to fatal outcome.
2. Lung inflammation relapse associated with glucocorticoids withdrawal happened in 4 (40%) pts at 66 (61,5; 70,5) day from COVID-19 start and in 1 case led to fibrosis development.
3. Bacterial complications, viz. subphrenic abscess of liver and bacterial pneumonia, happened in 2 (20%) pts at 87 and 170 days from the beginning of COVID-19 respectively. In both cases they were associated with prolonged glucocorticoids use (until 85 and 150 days from the beginning of COVID-19) and in 1 case led to fatal outcomes.
4. Myocarditis happened in 1 (10%) pt at 45 day from the COVID-19 beginning.

Conclusions: Pulmonary thromboembolism and lung inflammation were the most common reasons for the deterioration of COVID-pneumonia survivors and subsequent rehospitalization.