The number of COVID-19 cases and their severity vary between countries. COVID-19 also varies among individuals based on factors such as age, sex, and combinations. However, age is the factor with the highest correlation in COVID-19 cases and severity. Studies have shown that SARS-CoV-2 is particularly virulent in the elderly population, while children are less prone to the virus.
The majority of COVID-19 deaths occur in the elderly, with 90% of victims over the age of 70, and the child population is mostly unaffected by COVID-19. Although a more pronounced effect of COVID-19 is expected in the elderly, as their immune responses weaken with age, virulence of the virus appears to be associated with an unbridled immune response, and some patients appear to benefit from immunomodulatory drugs. Furthermore, it is not clear how neonates and infants with an adaptive immune system are relatively safe from COVID-19.
To study the role of reactive immunity against childhood vaccines in protection against COVID-19
Pedro A. Reche, an associate professor in the Faculty of Immunology and Medicine at the Complutense University of Madrid, recently examined the potential role of cross-reactive immunity in childhood vaccines and exposure to other human pathogens in protecting against COVID. 19. Professor Reche collected SARS-CoV-2-matched peptide batches in 25 human pathogen proteomes and vaccine antigens. The reactivity of these T and B cells was predicted to identify possible cross-reactive epitopes. The research is published in the journal Limitations in Immunology.
It has been shown that viruses that have undergone pediatric vaccines do not have a cross-reactive epitope for SARS-CoV-2, and that they cannot show protection against COVID-19. Also, common viruses, such as respiratory virus, rhinovirus, influenza virus, and various herpes viruses, are poor sources of immunity to reactivity against SARS-CoV-2. This demonstrates that the immune memory against these viruses cannot play any protective role in COVID-19. However, Research has found that combined vaccines such as the DTP vaccine – which are used to treat infectious diseases, diphtheria, tetanus and pertussis – can be important sources of reactive immunity to SARS-CoV-2.
A crucial link between the DTP vaccine and COVID-19 epidemiology
Cross-reactivity of DTP with SART-CoV-2 encompasses a large number of epitopes of CD8 and CD4 T cells that have protective coating and potentially neutralize B cell epitopes in the SARS-CoV-2 S protein. Globally, children receive a wide range of DTP vaccines, including 3-4 doses in the first year of life and one dose in 4-6 years. A low antigenic booster shot called Tdap is also given at 9-14 years of age. Thus, children can be protected against SARS-CoV-2 by cross-reactive immunity provided by these multiple DTP vaccines.
“These findings indicate that the cross-reactive immunity generated by DT antigens along with DTP vaccines is likely to protect COVID-19 in children and adolescents worldwide.”
The findings have shown that MenB vaccines can cause reactive cross-linked T cell immunity to SARS-CoV-2. However, they are unlikely to provide protection against SARS-CoV-2 in children, as Meningococcal B vaccines have recently been introduced, and this is not the case anywhere. In contrast, combined DTP vaccines have been widely used worldwide since the 1940s.
The severity of COVID-19 may be related to differences in DTP vaccination programs in different countries
According to Professor Reche, these findings indicate that the reactive cross-immunity provided by combined DTP vaccines is likely to be a relatively safe cause for children with COVID-19 worldwide. This cross-reactive immunity disappears over time in adults, explaining why COVID-19 cases and their severity increase with age.
“Cross-reactive immunity caused by DTP vaccines will eventually go away, explaining why COVID-19 cases and their severity increase with age.”
The global health crisis caused by the COVID-19 pandemic has led to tremendous efforts around the world to develop an effective vaccine against SARS-CoV-2, which is likely to take years. However, these results suggest that DTP vaccines, especially DTwP vaccines, could be used to protect the general population against SARS-CoV-2 by utilizing cross-reactive immunity induced by combined vaccines.
The author believes that due to the heterogeneity of DTP vaccines, COVID-19 severity and mortality in different countries may be related to differences in the composition of DTP vaccines and the onset of DTP vaccination programs.
“Given the heterogeneity of DTP vaccines, our results also suggest that COVID-19 mortality rates and severity may be related to differences in the composition of DTP vaccines, vaccine regimens, and initiation of DTP vaccination programs in different countries.”