The Fittest Variant?

The delta Covid19 variant, first identified in India, is currently the 'fittest' version of the Sars-Cov-2 virus. This variant has now been recorded in circa 92 countries. Research has found that 99% of new Covid19 infections in the UK are the delta variant. This variant may be 60% more transmissible than its alpha ('Kent') counterpart. Delta is probably linked to a greater risk of hospitalisation and may be somewhat more resistant to vaccines (https://www.theguardian.com/world/2021/jun/27/delta-covid-variant-may-be-edging-race-against-vaccines). So, what accounts for the delta variant's greater transmissibility? It could be the case, that people infected with delta, carry a higher viral load. They could release more virus, as they breathe and speak. Alternatively (or in addition), people may need to be exposed to fewer viral particles from delta to become infected. Finally, a shorter period of exposure may be needed for viral transmission. Data from Sydney (Australia), suggests 'scarily fleeting' encounters, of 5-10 seconds, may be sufficient to pass on the delta variant. People, just walking past a carrier, could be infected. The general advice, from WHO and others, is to 'play it safe' by trying to keep transmission low, whilst rolling out vaccination. Vaccine hesitancy seems to be fading in the UK (but not in some other countries). Vaccination uptake isn't helped by newspaper reports, that most people in England who currently die with Covid19 have been vaccinated. Spiegelhalter and Masters (https://www.theguardian.com/theobserver/commentisfree/2021/jun/27/why-most-people-who-now-die-with-covid-have-been-vaccinated) point out that this is hardly remarkable, in a country, where most adults have been vaccinated. Fewer people now die but vaccination doesn't give complete protection (somewhat negating the logic of the clamour for 'vaccination passports'). An 80 year old, who is vaccinated, carries about the same risk of dying from a Covid19 infection, as a 20 year old without the jab. If pockets of high Covid19 infection persist in areas of the world with low vaccination rates, delta will be superceded by an even fitter (and more dangerous) variant.