An under trial COVID-19 vaccine, analyzed by Sahin and colleagues, showed evident development of neutralizing antibodies and CD-8 response. However, the mRNA vaccine-induced B-cell response reached its highest two weeks after immunization and then declined afterwards.(14)
The effect of SARS-COV-2 vaccine on the body’s immune response was analyzed subsequent to the administration of two doses; the viral-induced antibody concentration seemed to diminish typically around day 43. This finding was in concordance with the results that Wu and Long et al have illustrated in response to the infection, thus clearly providing evidence of the feeble B-cell response to infection as well as vaccination. (5,6)
The memory B cells produced during the primary immune response are specific to the antigen involved during the first exposure; in a secondary response, the memory B cells specific to the antigen or similar antigens will respond. When memory B cells reencounter their specific antigen, they proliferate and differentiate into plasma cells, which then respond to and clear the antigen; such clearance is achieved by what is called the secondary antibody response. It is regarded that that secondary antibody response is the most crucial event that can prevent re-infection with a certain pathogen.(15)
In this context, Kapasi and colleagues tested the secondary antibody response reflective of B cell memory in old vs. young mice in response to bouts of exercise. Secondary antibody response appeared to be exercise dependent, because old mice that received 1 bout of intense exercise demonstrated increased anti-antibody levels compared with old non-exercising mice. Moreover, the old mice that received the booster immunization after undergoing 1 bout of intense exercise, have attained levels of anti-HSA antibodies comparable to those seen in the young mice. In accordance with our findings, Long and colleagues have tested the vaccine responses of two groups of old aged individuals. They have succeeded in showing that antibodies in response to pneumococcal vaccine improved significantly following regular moderate intensity exercise.(16)
Such findings signify that exercise has the ability to not only improve the outcome of infected cases but to prevent re-infection and can improve the response of vaccinated individuals. This should be taken into account during the ongoing trials for a potential COVID-19 vaccine.
Another important concern, during development of the vaccine is the severity of re-infection when compared to the initial infection. As shown in Table 1 as well as Figure 2 that >50% of reported re-infected cases are showing a more severe spectrum of the disease. This should be viewed with extreme caution in conjunction with Sahin et al findings of augmented systemic adverse reactogenicity after the second dose. Reactogenicity is the series of adverse local or systemic reactions after vaccination. It is usually correlated with baseline serum levels of IL-6. (17)
In spite of reduced vaccine immunogenicity in old age due to insufficient B-cell memory, a number of studies, particularly those of Cowling and associates, illustrated that the local and, to a lesser extent, the systemic reactogenicity of vaccines increased in older adults. This finding could be attributed to the reduction of Soleus Muscle Protein SOCSP3 due to lack of exercise and sedentary lifestyle, noting that SOCSP3 acts to repurpose IL-6 from a pure pro-inflammatory to a rather regulatory cytokine role.(18)
Thus, exercise not only can improve the immunogenicity of a potential vaccine but can also decrease the severity of re-infection and the adverse reactogenicity of potential vaccines under development.