We read with interest ‘Seroprevalence of Lyme borreliosis in Finland 50 years ago’ [[1]Cuellar J. Dub T. Sane J. Hytönen J. Seroprevalence of Lyme borreliosis in Finland 50 years ago.Clin Microbiol Infect. 2019 Oct 14; (S1198-743X(19)30530-0)Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar]. The authors studied the Lyme borreliosis (LB) seroprevalence in Finland in the 1960s and 1970s through evaluation of immunoglobulin G (IgG) against Borrelia burgdorferi in historical serum samples. Despite its scientific and comprehensive, we want to point out some technical issues that ought to be discussed. The key point of this study was the stability of IgG antibodies for B. burgdorferi in long-term-storage serum samples, which were collected from different regions in Finland between 1966 and 1972 [[2]Knekt P. Rissanen H. Jarvinen R. Heliövaara M. Cohort profile: the Finnish mobile clinic health surveys FMC, FMCF and MFS.Int J Epidemiol. 2017; 46: 1760e1Crossref Scopus (21) Google Scholar]. The serum samples were stored at −20°C for more than 50 years. According to the authors, ‘For serum quality check, the IgG antibody level in 41 randomly selected samples was measured using an in-house ELISA towards varicella zoster virus (VZV). All but three samples contained detectable levels of VZV IgG antibodies, reflecting the VZV antibody levels in the population today.’ To check serum quality, VZV IgG antibodies of the serum samples were detected by an in-house ELISA. In this study, the serum samples were detected by Borrelia whole-cell sonicate screening test and further confirmed by C6 Lyme ELISA test and recomBead IgG 2.0 assay [[3]van Beek J. Sajanti E. Helve O. Ollgren J. Virtanen M.J. Rissanen H. et al.Population-based Borrelia burgdorferi sensu lato seroprevalence and associated risk factors in Finland.Ticks Tick Borne Dis. 2018; 9: 275-280Crossref PubMed Scopus (16) Google Scholar]. The VZV IgG antibodies did not fully reflect the stability of the IgG antibodies for B. burgdorferi. Furthermore, there are no reports that IgG antibody titres for VZV and B. burgdorferi remain stable during long-term storage. Although the serum samples were stored at −20°C, the IgG antibody titres may degrade after 50 years. To minimize antibody degradation, the serum samples should be transferred as several separate aliquots in cryotubes and stored in cold-chain or liquid nitrogen from collection to transportation. These processes should be undertaken under sterile conditions. The samples should subsequently be placed at −70°C or −80°C for long-term storage before laboratory analysis. The collection and preparation of the serum samples in each district and transportation to the lab should take an average of 5 to 7 days [[4]Burimuah V. Sylverken A. Owusu M. El-Duah P. Yeboah R. Lamptey J. et al.Sero-prevalence, cross-species infection and serological determinants of prevalence of bovine coronavirus in cattle, sheep and goats in Ghana.Vet Microbiol. 2020; 241: 108544Crossref PubMed Scopus (12) Google Scholar]. Notably, the relationship between IgG antibodies for B. burgdorferi and storage conditions needs further investigation [[5]Zhao J. A comment on ‘Factors influencing the outcome of primary immunization against rabies in young dogs.Vet Microbiol. 2019; 228: 259Crossref PubMed Scopus (7) Google Scholar]. On the one hand, if the seropositive samples for B. burgdorferi from this study are still being stored, we strongly believe that they should be tested by the same methods in the future [[1]Cuellar J. Dub T. Sane J. Hytönen J. Seroprevalence of Lyme borreliosis in Finland 50 years ago.Clin Microbiol Infect. 2019 Oct 14; (S1198-743X(19)30530-0)Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar]. On the other hand, the LB seroprevalence among the general population was investigated in Finland in 2011 [[3]van Beek J. Sajanti E. Helve O. Ollgren J. Virtanen M.J. Rissanen H. et al.Population-based Borrelia burgdorferi sensu lato seroprevalence and associated risk factors in Finland.Ticks Tick Borne Dis. 2018; 9: 275-280Crossref PubMed Scopus (16) Google Scholar]. If the serum samples were stored at −20°C till now, the seropositive samples should be detected now to investigate the stability of IgG antibodies for B. burgdorferi after 9 years' storage. The collection, preparation, transportation and storage conditions of the serum samples should be described in the Materials and Methods sections of future seroprevalence studies of LB. Financial support was received from the Foundation of Liaocheng University (grant 318011907) and the Doctoral Foundation of Liaocheng University (grants 318051738 and 318051827). All authors report no conflicts of interest relevant to this article. Seroprevalence of Lyme borreliosis in Finland 50 years agoClinical Microbiology and InfectionVol. 26Issue 5PreviewLyme borreliosis (LB) is a tick-borne infection common in Europe. In Finland, the LB seroprevalence in the healthy population was 3.9% in 2011. While the present-day seroprevalence of LB is well characterized in several European areas, there are no studies on the seroprevalence of LB before the description of the infection in the late 1970s. Full-Text PDF Open Access'Seroprevalence of Lyme borreliosis in Finland 50 years ago' – Author’s replyClinical Microbiology and InfectionVol. 26Issue 7PreviewWe read with keen interest the comments on ‘Seroprevalence of Lyme borreliosis in Finland 50 years ago.’ Zhang et al. questioned the effect of long-term storage on the stability of Borrelia antibodies in serum samples. Further, they suggested retesting the Borrelia antibodies in the serum samples collected in 2011. Full-Text PDF Open Archive