This is a follow-up on an earlier question regarding mechanistics of vaccines: why current vaccines don't block transmission. In summary, they don't engage mucosal immune cells to produce IgA. Thus, they induce production of IgG by systemic B cells and can lower viral load, but not block viral shedding or uptake through mucous membranes. "Herd immunity" is dependent on halting transmission. So, the AstraZeneca trials were the only ones that assessed sterilizing immunity. Their surrogate for transmission was asymptomatic cases. They found that their LD/SD regimen was about 60% effective in blocking new asymptomatic cases. My first question, then: was this simply due to a reduced viral load (and reduced coughing perhaps) which was expressed as a lower transmission rate? Can this even be equated with measles-type herd immunity? My second question is would this 60% effectiveness at blocking asymptomatics on the basis of reduced viral load be sufficient to achieve herd immunity?
i hope this article can help.
https://www.researchgate.net/publication/343443540_Investigating_Virological_Immunological_and_Pathological_Avenues_to_Identify_Potential_Targets_for_Developing_COVID-19_Treatment_and_Prevention_Strategies
Herd immunity you obtain at 80% vaccination. It may depend on several factors, although you are kind of right when how contagious and viremia are related. You may be able to transmit very quickly, but maybe the viremia is very low. The viremia may depend on the time taken for the disease to appear but it may be low or high. Maybe you infected having low viremia. Maybe say a high viremia would be a peak on a immune response. You may transmit very quickly or maybe by transmitting, it may take some time for the first symptoms to appear. Maybe the virulence is so high that maybe there is no spreading. What I don't know if you set measles for a reason. It is very contagious and it does so very quickly.
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