en Health Protection including control of communicable and non-communicable diseases Health Protection including control of communicable and non-communicable diseases پژوهشي Research Article <span style="font-size:12pt"><span style="line-height:16.0pt"><span new="" roman="" style="font-family:" times=""><b><i><span style="font-size:9.0pt">Background & Aims</span></i></b><b><span style="font-size:9.0pt">: </span></b><span style="font-size:9.0pt">Investigating re-infection with COVID-19 is necessary due to the existence of genetic differences among populations after a general vaccination plan. In addition to genetic differences, gender, age, the presence of underlying diseases, and the type of vaccine are factors that affect the rate and severity of re-infection after vaccination. </span></span></span></span><br> <span style="font-size:12pt"><span style="line-height:16.0pt"><span new="" roman="" style="font-family:" times=""><b><i><span style="font-size:9.0pt">Materials & Methods</span></i></b><b><span style="font-size:9.0pt">:</span></b> <span style="font-size:9.0pt">Demography, physical activity and nutrition, underlying diseases, the period of involvement with the COVID-19 pandemic, and the percentage of re-infection before and after each stage of vaccination of the medical staff at Imam Khomeini Hospital in Ardabil (Iran) were evaluated. Our study was performed in a descriptive-analytical manner among 149 healthcare workers. The data were collected using a valid and reliable questionnaire and analyzed using SPSS version 26.</span></span></span></span><br> <span style="font-size:12pt"><span style="line-height:16.0pt"><span new="" roman="" style="font-family:" times=""><b><i><span style="font-size:9.0pt">Results</span></i></b><b><span style="font-size:9.0pt">:</span></b><span style="font-size:9.0pt"> According to the results, 69.1% of healthcare workers had a positive PCR test or symptoms of COVID-19 before the first injection of the vaccine. The types of injected vaccines included AstraZeneca, Sinopharm, Sputnik V, Bharat, Barekat, Spicogen, and PastoCovac. After the injection of the first dose of the vaccine, the number of severe cases decreased from 30.9% to 10.7%, which indicates the effectiveness of the vaccination. </span></span></span></span><br> <span style="font-size:12pt"><span style="line-height:16.0pt"><span new="" roman="" style="font-family:" times=""><b><i><span style="font-size:9.0pt">Conclusion</span></i></b><b><span style="font-size:9.0pt">: </span></b><span style="font-size:9.0pt">The lowest rate of re-infection was observed in people with good physical activity compared to those who were less active (9.6% versus 59.6%). The highest rate of re-infection with COVID-19 between the first and second doses of the vaccine was related to Sinopharm, Sputnik V, and AstraZeneca. The highest rate of re-infection (82.7%) was in the age group under 40 years old.</span></span></span></span> AstraZeneca, Breakthrough infection, COVID-19, Vaccine 306 323 http://hsm.umsu.ac.ir/browse.php?a_code=A-10-266-2&slc_lang=en&sid=1 Elham Rezaei elrezaeeph@gmail.com 10031947532846003055 10031947532846003055 Yes Students Research Committee, School of Paramedical Sciences, Ardabil University of Medical Sciences, Ardabil, Iran Shafagh Aliasgarzadeh dr.sh.aliasgarzadeh@gmail.com 10031947532846003056 10031947532846003056 No Department of Internal Medicine, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran Sevda Mikaeili mirak sevda.mikaeili.m@gmail.com 10031947532846003057 10031947532846003057 No Department of Clinical Pharmacy, School of Pharmacy, Ardabil University of Medical Sciences, Ardabil, Iran Faraz Tayyar-Iravanlou Faraztayyar97@gmail.com 10031947532846003058 10031947532846003058 No Department of Psychiatric Nursing, School of Nursing and Midwifery, Urmia University of Medical Sciences, Urmia, Iran.