“The Covid-19 vaccines have not delivered in terms of preventing infection and transmission. These products clearly do not prevent transmission. They should never have been expected to, by virtue of their mechanism of action (i.e. the creation of blood-borne antibodies, when – as with other respiratory viruses – the primary immune defenses reside in the mucous membranes lining the upper respiratory tract and lungs).”
With this statement you are suggesting that mucosal C-19 vaccines may do the job. This is not correct. There is no evidence whatsoever that mucosal vaccines would prevent immune escape when administered during a pandemic. There is no evidence either that any (experimental) mucosal vaccine works better than the same vaccine administered intramuscularly or subcutaneously (even for pathogens entering via mucosal membranes). That’s why the spectrum of commercialized mucosal vaccines is scarce. It’s not because a respiratory pathogen invades the body via the mucosa that mucosal vaccine administration is more efficacious. It’s also a complete misunderstanding that systemic antibodies do not reach the mucosa (they actually do via transudation). In addition, to maintain high titers of neutralizing IgA, regular booster doses (every 3-4 months) are required. But even then, one will not avoid immune escape when these vaccines are used during a pandemic.
I am reacting to this statement as it provides grist to the mill of those who remain convinced that we can vaccinate ourselves out of the pandemic. The real reason as to why C-19 vaccines cannot prevent infection or transmission is because they don’t induce sterilizing immunity. Vaccine-induced Abs cannot sterilize the virus when the immune system gets already exposed to the virus while it is still in the process of mounting an antibody (Ab) response. It takes time for these Abs to become fully functional (neutralizing capacity) and reach a high enough concentration to neutralize the virus. As long as the humoral response is insufficient/ immature, the Abs exert suboptimal immune pressure on viral infectiousness. This will lead to natural selection and dominant propagation of more infectious variants. This increases viral infectivity and promotes viral transmission instead of reducing it. I understand that PANDA is not a science-oriented organization but that should not be an excuse to make statements that are scientifically incorrect. Those may be easier for the public to understand but eventually lead to confusion and may even encourage another bunch of nonsensical initiatives.
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