The virus currently relies on the mobility of asymptomatically or mildly infected Covid-19 vaccinees for inter-host transmission. However, as circulating variants become more infectious, their progeny is increasingly ‘neutralized’ by upper respiratory tract (URT)-patrolling migratory dendritic cells (DCs; see Figure below). This can drive the natural selection of highly virulent immune escape lineages because high virulence implies rapid spread from the many virus-loaded migratory DCs to susceptible organ cells (a phenomenon called ‘trans infection’), which is associated with more aggressive replication. In this case, the virus can bypass the need for host mobility (i.e., inter-host transmission) and instead rely on the virus’s ‘mobility’ for inter-organ (i.e., intra-host) transmission.
The way I think the viral dynamics are going to evolve is that during this summer inter-host transmission of highly infectious variants is actually going to increase due to a rapid succession of newly emerging, more infectious immune escape variants combined with frequent contacts among asymptomatically/ mildly infected vaccinees. This will lead to a rapidly increasing majority of highly C-19 vaccinated populations sitting on suboptimal virulence-inhibiting Abs (the so-called 'polyreactive non-neutralizing Abs' or PNNAbs). This implies that in this rapidly "immune homogenized" population, highly virulent mutants generated during viral replication could suddenly undergo "massive" (i.e., population-level) immune selection, leading to a dramatic surge in cases of severe disease enhancement in highly C-19 vaccinated regions.
In conclusion: Even if high virulence hampers traditional inter-host transmission, evolutionary immune pressure on viral trans infection could favor natural selection of coronavirus strains with higher virulence. This is especially true if intra-host transmission allows the virus to bypass the need for host mobility, as the incapacitation of the host significantly reduces transmission opportunities. This could allow highly virulent coronavirus strains to replicate effectively within hosts, even if the host is severely ill and immobile…
Africa will win…
Geert Vanden Bossche received his DVM from the University of Ghent, Belgium, and his PhD degree in Virology from the University of Hohenheim, Germany. He held adjunct faculty appointments at universities in Belgium and Germany. After his career in Academia, Geert joined several vaccine companies (GSK Biologicals, Novartis Vaccines, Solvay Biologicals) to serve various roles in vaccine R&D as well as in late vaccine development.
Geert then moved on to join the Bill & Melinda Gates Foundation’s Global Health Discovery team in Seattle (USA) as Senior Program Officer; he then worked with the Global Alliance for Vaccines and Immunization (GAVI) in Geneva as Senior Ebola Program Manager. At GAVI he tracked efforts to develop an Ebola vaccine. He also represented GAVI in fora with other partners, including WHO, to review progress on the fight against Ebola and to build plans for global pandemic preparedness.
Back in 2015, Geert scrutinized and questioned the safety of the Ebola vaccine that was used in ring vaccination trials conducted by WHO in Guinea. His critical scientific analysis and report on the data published by WHO in the Lancet in 2015 was sent to all international health and regulatory authorities involved in the Ebola vaccination program. After working for GAVI, Geert joined the German Center for Infection Research in Cologne as Head of the Vaccine Development Office. He is at present primarily serving as a Biotech / Vaccine consultant while also conducting his own research on Natural Killer cell-based vaccines.
Email: info@voiceforscienceandsolidarity.org
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