SÜMBÜL, BİLGESumbul, Hilmi ErdemOKYAY, RAMAZAN AZİMGulumsek, ErdincŞAHİN, AHMET RIZABoral, BarisKocyigit, Burhan FatihAlfishawy, MostafaGold, JeffreyTasdogan, Ali Muhittin2021-03-162021-03-162021-02-01SÜMBÜL B., Sumbul H. E. , OKYAY R. A. , Gulumsek E., ŞAHİN A. R. , Boral B., Kocyigit B. F. , Alfishawy M., Gold J., Tasdogan A. M. , -Is there a link between pre-existing antibodies acquired due to childhood vaccinations or past infections and COVID-19? A case control study-, PEERJ, cilt.9, 2021http://hdl.handle.net/20.500.12645/28591https://peerj.com/articles/10910/Background: There is growing evidence indicating that children are less affected from COVID-19. Some authors speculate that childhood vaccinations may provide some cross-protection against COVID-19. In this study, our aim was to compare the circulating antibody titers for multiple childhood vaccine antigens, as an indicator of the state of immune memory between patients with COVID-19 and healthy controls, with a specific aim to identify the association between disease severity and antibody titrations which may indicate a protective function related to vaccine or disease induced memory. Methods: This study is a case-control study including 53 patients with COVID-19 and 40 healthy volunteers. COVID-19 severity was divided into three groups: asymptomatic, mild and severe. We measured the same set of antibody titers for vaccine antigens, and a set of biochemical and infection markers, in both the case and control groups. Results: Rubella (p = 0.003), pneumococcus (p = 0.002), and Bordetella pertussis (p < 0.0001) titers were found to be significantly lower in the case group than the control group. There was a significant decline in pneumococcus titers with severity of disease (p = 0.021) and a significant association with disease severity for Bordetella pertussis titers (p = 0.014) among COVID patients. Levels of AST, procalcitonin, ferritin and D-dimer significantly increased with the disease severity. Discussion: Our study supports the hypothesis that pre-existing immune memory, as monitored using circulating antibodies, acquired from childhood vaccinations, or past infections confer some protection against COVID-19. Randomized controlled studies are needed to support a definitive conclusionCOVID-19Cross-protectionPandemicAntibody titersArticleWOS:0006164068000168510092811310.7717/peerj.1091033614298