Introduction: The COVID-19 global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) began in December 2019 in Wuhan, China and has spread worldwide. Healthcare workers play a key role in this pandemic to provide ongoing care for large numbers of COVID-19 patients. Frontline healthcare personnel are 3.4 times more likely to become infected than the general population. In this study, it was aimed to determine the pre- and post-vaccine infection rates in healthcare workers of a 3rd level training and research hospital.

Material and Method: There are a total of 1582 healthcare workers in our hospital. There are 356 doctors, 689 nurses, 34 technicians, 207 cleaning personnel, 262 medical secretaries and 34 security personnel. In the diagnosis of acute infection it is recommended to demonstrate the presence of viral RNA in respiratory tract clinical samples (nasopharyngeal swab, tracheal aspirate, Broncho alveolar lavage, sputum) by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR). The treatments were arranged according to the Covid 19 Guidelines of the Ministry of Health in accordance with the 2020 update. Covid 19 vaccination statuses were obtained retrospectively from the employee health data of our hospital.

Results: Between March 1 and September 1 2021, a total of 468 people were infected. Before Covid 19 vaccine came to our country, the infection of healthcare workers were 52 doctors, 150 nurses, 60 cleaning staff, 26 laboratory technicians, 20 medical secretaries and 9 security guards. After Covid 19 vaccine of healthcare workers, Covid 19 PCR test of 78 people was positive. After the dose, 73 people (52 women, 21 men) were positive for Covid 19 PCR for an average of 50.9 days. 1 doctor (7th days after 2 sinovac vaccine), 1 nurse (7th day after 2nd sinovac vaccine) were admitted to the Covid service. 42 UK variants detected; 7 physicians (all 2 doses vaccinated) infected on average 55 days (4 females, 3 males) after 2nd dose vaccination. South African variant was seen in 5 people. 3 nurses (3 females) were detected 35 days after the 2nd dose of vaccine, and 1 of 2 security personnel (1 female, 1 male) was detected 46 days after the 2nd dose of vaccination.

Conclusion: Healthcare workers are at high risk of exposure to coronavirus disease-2019 (COVID-19), with priority given to COVID-19 vaccine during the pandemic.

The virus is transmitted from person to person by droplet route and close contact, and after an incubation period of 5.2 days (2-14 days), it is often asymptomatic, but fever, cough, fatigue, shortness of breath, headache, sore throat, and runny nose, taste/odor it may progress with non-specific symptoms such as loss of sensation, diarrhoea, and haemoptysis [1,2]. The COVID-19 vaccine is the most effective way to control the pandemic and there are different types of vaccines. As of January 13, 2021, Turkey granted emergency use permission to 'Corona Vac' produced by the Chinese biopharmaceutical company Sinovac. Corona Vac is a chemical developed against SARS-CoV-2 It is an inactivated vaccine [3,4]. Corona Vac was the only vaccine available in the country. More than a million healthcare workers (more than 95% of all healthcare workers) received their first dose within a week. It started with healthcare workers on January 14, 2021. Vaccination was done with two doses of Corona Vac, 4 weeks apart.

The vaccination schedule is two doses of 3 mcg 28 days apart. Healthcare professionals had their second dose of vaccine administered in mid-February 2021 [5]. With the arrival of Biontech vaccine in our country on June 30, 2021, healthcare workers continued to be vaccinated (1 vial (0.45 ml) of 6 doses (each dose contains 30 micrograms of BNT162b2 mRNA in lipid nanoparticles). Descriptive statistics (mean, median, std. deviation, etc.) were used for continuous numerical variables in the analysis. Categorical variables are expressed as numbers and percentages in frequency tables. Group distributions of categorical variables are shown in numbers and percentages using crosstab statistics. The statistical significance limit was taken as p<0.05. SPSS 21 program was used for statistical analysis [6-8].

A total of 1582 healthcare workers are in our hospital. There are 356 physicians, 689 nurses, 34 technicians, 207 cleaning staff, 262 medical secretaries, and 34 security personnel. Starting from March 1, 2020 until September 1, 2021, 468 people were infected (Tables 1,2).

Table 1: COVID 19 infection numbers by occupational group of healthcare professionals before Coronavac Vaccine.

Healthcare workers working in hospitals constitute a high-risk group during the epidemic. Healthcare workers' risk of infection may increase during an ongoing outbreak due to a variety of factors, including continued exposure to patients, lack of personal protective equipment, and inadequate infection control training. During the 2003 severe acute respiratory syndrome (SARS) epidemic in Hong Kong, the first major cluster of transmission occurred at the Prince of Wales Hospital, where healthcare workers accounted for a significant portion of the infection, with 43.6% of cases admitted to this hospital.8 Protecting healthcare workers from infection plays a crucial role in controlling hospital-acquired transmission. In addition, healthcare professionals were a reliable source of information about vaccines for patients [9]. In our country, 273,000 people had COVID-19 until September 2020, and it was announced that 29 865 of them were healthcare professionals [10-12]. In a phase 3 randomized controlled study conducted in 12 688 individuals in Brazil, 14 days after 2 doses of vaccination on days 0-14, it was reported that the vaccine's protection against symptomatic COVID-19 was 51% and protection against hospitalization was 100% [13]. In Turkey 0-14 in a phase 3 randomized controlled trial in 13 000 people it has been reported that 14 days after 2 doses of vaccination on days 2, the protection against symptomatic COVID-19 of the vaccine was 84% and the protection against hospitalization was 100% [14]. Before healthcare workers of our hospital were vaccinated, 317 people (20%) had covid 19 infection. 5 people (0.3%) after the 1st dose of vaccination, 73 people (4.6%) became infected after second dose. The hospitalization rate was 1.4% (n: 23) in the unvaccinated and 0.1% (n: 2) on the 7th day of the second dose of vaccine. The UK variant emerged in the UK in September 2020 and was found to contain multiple mutations. This variant has been noted to spread more easily and quickly than other variants and has since been detected in many countries around the world [15]. 42 UK variants were detected in our healthcare workers; 7 physicians (16%) became infected for an average of 55 days (4 females, 3 males) after receiving the second dose of vaccine. The UK variant was detected in 18 nurses (42%). 8 people had received 2 doses of vaccine. It was after 59.2 days on average. (7 females, 1 male), 5 technicians (12%); 2 technicians, 2 persons (2 females) who received the 2nd dose vaccine after 34 days, 3 medical secretaries (7%); 1 medical secretary 2nd dose 1 male after 55.6 days on average, 2 security workers (5%); 1 security worker 31 days after 2nd dose, 7 cleaning staff (18%) vaccinated; 4 subjects (1 female, 3 males) developed a UK variant infection 70.2 days after second dose of vaccine. The South African variant arose independently of other variants and was first identified in early August 2020. It has been reported that it shares some mutations with the UK variant, and similarly, this variant is more contagious than the original virus [15]. In our study, the South African variant was detected in 3 nurses (60%) an average of 35 days after the second dose of vaccine, and 46 days after the second dose in 1 of 2 security workers (40%). It has been noted that most of the employees diagnosed with COVID-19 had only mild or nonspecific symptoms during the clinical trial. Early and non-specific symptoms are difficult to identify, so healthcare professionals may inadvertently infect vulnerable patients or other personnel [16].

As a result, COVID 19 remains a threat to the entire world. Vaccination, personal and social measures will increase the chances of success in the fight against Covid 19. Although it cannot completely prevent the disease, the prevention of critical illness and death should be considered a great success for vaccines. Any symptoms of COVID-19 found among vaccinated healthcare workers should not be considered vaccine-related events, and these healthcare workers should be considered suspected COVID-19 cases until COVID-19 infection has been ruled out. In addition, active and passive surveillance and routine laboratory testing are necessary to identify COVID-19 among healthcare workers, even if they are vaccinated, to prevent transmission to other healthcare workers and healthcare settings. The importance of promoting vaccination among healthcare workers has been recognized.

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