الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
SUMMARY
Some COVID-19 patients have become reinfected with the virus with the continuation of the COVID-19 pandemic. Viral gene sequencing has found that some of these patients were reinfected by the different and others by same strains. This has raised concerns about the effectiveness of immunity after infection and the reliability of vaccines.
This retrospective cohort study was conducted on 400 patients with COVID-19 confirmed infection & admitted to Ain Shams University Hospitals to effectiveness of COVID-19 vaccine.
Regarding sociodemographic, among the 400 included subjects, 49.00% were females and 51.00% were males. Their age ranged between 16-85 years with a mean value of 52.6 ± 14.12 years. Most of them have severe condition on admission 76.75% and 6.50% were critical. The comorbidity rate was 15.50%, and 4.25% were currently smokers, while 1.75% were ex-smokers. The duration of hospital admission ranged between 1-36 days with a mean value of 7.488±5.263 day.
Concerning clinical data, Out of the 400 included subjects, 29 of them need ICU admission (7.25%). Indication for ICU referral was hypoxia in 26 subjects (6.50%) followed by dyspnea in 2 cases (0.50%) and chest pain in 1 case (0.25%). Only 1 patient need mechanical ventilation (0.25%). All of them survived and discharged from hospital.
As regard comorbidities among our included subjects, the commonest comorbidity was DM in 10% followed by HTN in 6.5% then respiratory diseases and obesity in 3% for each and cardiac diseases in 1.75%. None of them has Hematological disease, chronic Kidney disease, malignancy, organ transplantation or was pregnant.
According to vaccination status, the current study detected that 340 out of the 400 included subjects received COVID vaccination (85%); 4.41% received incomplete doses, 67.06% received full vaccination with 28.23% received full vaccination with additional booster dose. 53.61% of booster vaccination was by the same vaccine each time while 46.39% received different vaccines.
With reference to re-infection characteristics of the studied population, the present study detected that among our included subjects, 59 of them reported COVID-19 re-infection (14.75%). Re-infection was diagnosed by symptoms in 57.6% and based on clinical diagnosis in 20.33% while only 22.03% were confirmed by PCR test. The number of re-infections was once in 72.88% and more than once in 20.33%. Time period between vaccination & re-infection; 23.40%were with in vaccine effective period (6 month), 38.30% were after vaccine effective period (>6 month), while 38.30% of subjects did not recall the date of reinfection. Four subjects need readmission to hospital and only 1 need admission to ICU.
With reference to Comparison between vaccinated and not vaccinated groups (N=400), There is no statistically significant difference between vaccinated and non-vaccinated subjects as regard sex and the presence of comorbidities.
There is a statistically significant difference in vaccination rate between working and not working. Although the reinfection rate among the vaccinated group was 13.82% and that among the non-vaccinated group was 20.00%, there is no statistically significant difference between vaccinated and non-vaccinated subjects as regard reinfection and hospitalization frequency. The duration of hospital admission during re-admission ranged between 5-7 days (6 days for non-vaccinated person and mean value of 6 ± 1 days in vaccinated persons).
Comparison between reinfected and not reinfected patients (N = 340), There is no statistically significant difference between vaccinated re-infected and vaccinated not re-infected subjects as regard age, sex, job and the presence of comorbidities. Reinfection after vaccination was more frequent in working than not working subjects