Table 1.
Analytical observational studies from the beginning of COVID-19 to August 2022.
| No. | Country | Publication Date | Author | Title | Findings |
|---|---|---|---|---|---|
| 1 | Italy | May 2022 | Sacco et al. [24] | Risk and protection factors for SARS-CoV-2 reinfections | Not being vaccinated emerges as the most significant risk factor. The risk of infection escalates 18 times more with the Omicron variant. Individuals who have experienced a severe initial infection and are over 60 years of age face heightened risks. |
| 2 | Italy | May 2022 | Flacco et al. [25] | Risk of SARS-CoV-2 reinfection 18 months after primary infection: a population-based observational study | Risk is significantly higher in women, young people, and people who have not been vaccinated. |
| 3 | Saudi Arabia | April 2022 | Shaheen et al. [26] | COVID-19 reinfection: a multicenter retrospective study in Saudi Arabia | Among the 35,288 analyzed patients, 0.37% experienced reinfection. The mean age of the participants was 40.95 ± 19.48 years, and 50.76% were female. |
| 4 | Sweden | April 2022 | Nordström et al. [27] | Risk of SARS-CoV-2 reinfection and hospitalization from COVID-19 in people with natural and hybrid immunity: a retrospective total population cohort study in Sweden | Two doses of the SARS-CoV-2 vaccine were associated with a 66% lower risk of reinfection. |
| 5 | USA | August 2021 | Slezak et al. [28] | Rate and severity of suspected reinfection by SARS-CoV-2 in a cohort of PCR-positive COVID-19 patients | Out of 75,149 cases, only 315 suspected reinfections were identified. Significant independent predictors of suspected reinfection included being a woman, an adult, being immunocompromised, and having previously been hospitalized for COVID-19. |
| 6 | England | April 2022 | Mensah et al. [29] | Illness severity during SARS-CoV-2 reinfection: a nationwide study | The female sex represented the highest proportion of reinfections (67%). Evidence suggested a rising increase in the risk of infection in individuals over 70 years of age. |
| 7 | China | December 2020 | Yao et al. [30] | Factors associated with a recurrence of SARS-CoV-2 after hospital discharge among patients with COVID-19: systematic review and meta-analysis | The primary factors associated with the recurrence of COVID-19 after hospital discharge included advanced age, severity of the previous infection, bilateral pulmonary infiltration, and decreases in leukocyte, platelet, and CD4+ T counts. |
| 8 | South Africa | March 2022 | Pulliam et al. [31] | Increased risk of reinfection by SARS-CoV-2 associated with the emergence of Omicron in South Africa | The relative risk of reinfection by COVID-19 increased with the third wave, marked by the emergence of the Omicron variant. |
| 9 | Bahrain (Middle East) | August 2022 | Almadhi et al. [3] | Epidemiological evaluation of reinfection by SARS-CoV-2 | The proportion of reinfected males was significantly higher at 60.3% (p < 0.0001), particularly within the 30–39 age group (29.7%). The lowest number of episodes occurred between 3 and 6 months after the first infection (20.6%), while the highest number of episodes occurred from the 9th month after the previous infection (46.4%). |
| 10 | Saudi Arabia | July 2022 | Al-Otaiby et al. [32] | SARS-CoV-2 reinfection rate and outcomes in Saudi Arabia: a national retrospective study | In the analysis of the risk factors, reinfection was highly associated with comorbidities, including HIV, obesity, and being healthcare personnel. |
| 11 | Mexico | April 2021 | Murillo-Zamora et al. [33] | Predictors of severe laboratory-confirmed symptomatic SARS-CoV-2 reinfection | Factors associated with an increased risk of severe symptomatic SARS-CoV-2 reinfection included a history of laboratory-confirmed severe coronavirus disease. |
| 12 | Mexico | May 2021 | Garduño-Orbe et al. [34] | SARS-CoV-2 reinfection in health workers in Mexico: Case report and review of the literature | Two out of the four cases of reinfection were severe, while in the remaining cases, the clinical manifestations resembled those of the previous infection. |
| 13 | Spain | January 2022 | Sánchez-Varela et al. [35] | Reinfection by the Omicron variant in patients previously performed with the Delta variant of the SARS-CoV-2 coronavirus: an increasingly frequent reality in primary care | Increased incidence due to the Omicron variant |
| 14 | China | May 2020 | Hu et al. [36] | Recurrent positive reverse transcriptase–polymerase chain reaction results for coronavirus disease 2019 in patients discharged from a hospital in China | There were no significant differences between the demographic and baseline clinical characteristics in the recurrence and non-recurrence groups. |
| 15 | Republic of Cyprus | March 2022 | Quattrocchi et al. [37] | Effect of vaccination on the risk of reinfection by SARS-CoV-2: a case-control study in the Republic of Cyprus | Their findings support the benefit of vaccination for individuals previously infected with SARS-CoV-2. |
| 16 | USA | August 2021 | Cavanaugh et al. [38] | Reduced risk of reinfection with SARS-CoV-2 after vaccination against COVID-19 in Kentucky, May–June 2021 | Those not vaccinated were from 2.3 to 4 times more likely to be reinfected compared to those who received all vaccinations (odds ratio (OR) = 2.34; 95% confidence interval (CI) = 1.58–3.47). In individuals with prior infection, full vaccination provided additional protection against reinfection. |
| 17 | Serbia | July 2022 | Medić et al. [39] | Risk and severity of SARS-CoV-2 reinfections during 2020–2022 in Vojvodina, Serbia: a population-level observational study | Those who were not vaccinated (OR = 1.23; 95% CI = 1.14–1.33), those with incomplete vaccination (OR = 1.33; 95% CI = 1.08–1.64), or fully vaccinated individuals (OR = 1.50; 95% CI = 1.37–1.63) were more likely to experience reinfection compared to patients who received the booster dose. |
| 18 | Austria | February 2021 | Pilz et al. [40] | Risk of SARS-CoV-2 reinfection in Austria | A relatively low risk of reinfection was documented. Patients with reinfections were of both sexes, spanning a wide age range, and were hospitalized during both infections. |
| 19 | Brazil | February 2021 | Adrielle Dos Santos et al. [41] | Recurrent COVID-19 including evidence of reinfection and increased severity in thirty Brazilian healthcare workers | Out of 33 patients with recurrent COVID-19, 26 were women, and 30 were healthcare workers. The median time to recurrence was 50.5 days. |
| 20 | Sweden | January 2020 | Havervall et al. [42] | Robust humoral and cellular immune responses and low risk of reinfection at least 8 months after asymptomatic or mild COVID-19 | The presence of IgG anti-spike antibodies is associated with a significantly reduced risk of reinfection for up to 9 months following asymptomatic or mild COVID-19. |
| 21 | India | January 2022 | Nisha et al. [43] | Incidence of SARS-CoV-2 infection, reinfection, and post-vaccination and associated risks in healthcare workers in Tamil Nadu: a retrospective cohort study | Men and primary care providers were at a higher risk of infection. Partial vaccination status was identified as one of the determinants of reinfection. |
| 22 | USA | May 2022 | Levin-Rector et al. [44] | Reduced odds of SARS-CoV-2 reinfection after vaccination among New York City adults, July–November 2021 | Vaccination decreased the likelihood of reinfections, particularly when the Delta variant predominated. |
| 23 | Several countries | August 2021 | Sotoodeh Ghorbani et al. [8] | Epidemiological characteristics of cases with reinfection, recurrence, and hospital readmission due to COVID-19: a systematic review and meta-analysis | The recurrence of reinfections was higher in women in comparison to men. Hospital readmission rates were similar for both sexes. There remains uncertainty regarding long-term immunity after SARS-CoV-2 infection. |
| 24 | France | March 2022 | Nguyen et al. [45] | SARS-CoV-2 reinfection and severity of COVID-19 | Reinfection represented 0.4% of the diagnosed positive cases. Among the 64 patients who underwent serological tests, 39 had antibodies when sampled early in their second infection. Only seven patients (3.4%) experienced infection twice with the same variant. |
| 25 | England | March 2022 | Mensah et al. [46] | Risk of SARS-CoV-2 reinfections in children: a prospective national surveillance study between January 2020 and July 2021 in England | Children were at a lower risk of reinfection compared to adults, and reinfections were not associated with more severe disease or fatal outcomes. |
| 26 | Mexico | June 2022 | Ochoa-Hein et al. [47] | Significant increase in SARS-CoV-2 reinfection rate in vaccinated hospital workers during the Omicron wave: a prospective cohort study | The SARS-CoV-2 reinfection rate increased significantly during the Omicron wave despite a high primary vaccination coverage rate. Nearly a third of reinfected individuals had received a booster vaccine at least 14 days before the last episode of COVID-19. |
| 27 | South Korea | August 2022 | Jang et al. [48] | SARS-CoV-2 reinfection in general population, South Korea: nationwide retrospective cohort study | Individuals with one dose of the vaccine had the highest reinfection rate at 642.2 per 100,000, followed by those not vaccinated (536.2/100,000) and individuals vaccinated with two doses (406.3/100,000). |
Source: Self-prepared based on the systematic review.