It seemed like a chimera in January, when the vaccination rate in Spain progressed slowly and we saw the first stoppages: they stopped inoculating the first doses to be able to ensure the second ones that were still pending. It seemed like a chimera in April, when the government first announced its specific objectives and it required a much greater speed than we had then.
The Government set itself the objective of reaching 33 million vaccinated, 70% of the Spanish population, “at the end of August” with four previous steps between May and July. Three of them were exceeded within the established period; the third, the fifteen million, was delayed for a few days. Now, September 1 (with the figures that refer to August 31), Spain has exceeded the target figure, the psychological barrier that we had been waiting for eight months. 33,376,693 have been fully vaccinated. More than 66 million doses have been administered.
LESS THAN 100 DAYS for GROUP IMMUNITY: Towards a FUTURE without PANDEMIC
And now, the nuances
That of 70% of the population was the figure that was originally considered adequate to achieve group immunity. To determine this figure, it is necessary to have several variables, the essential one being the basic reproductive number (R0), which indicates the transmissibility of the virus. At the beginning of the pandemic, with the variant that left Wuhan, it was estimated between 2 and 3. With this data, 70% was estimated as the necessary figure for that group immunity.
The problem is that during this time we have seen more contagious variants arrive, such as the British or Delta. The first was around 50% more infective than the original. The second is another 50% more contagious than Alpha, the British, reaching its Ro up to 8 or 9. This forces to rethink the calculations to achieve group immunity.
With that reproductive rate of the Delta variant, a minimum figure necessary for that group immunity would be 85%. France set it at 90%. The epidemiologist Javier del Águila spoke of it as practically impossible to achieve with a variant such as Delta, or in any case reaching 95% of the vaccinated population, for which it would also be necessary to vaccinate children.
He added that this is a figure “very difficult to reach” even in a country like Spain, with a very low reluctance to vaccines, in contrast to other countries that advanced at higher rates during the first months of the campaign but have been all summer practically stagnant before the refusal of a part of the citizenship to receive the vaccine.
For the moment, yes, something that no one will be able to take from us: between all of us (the central government, the autonomies that have health powers, a citizenry that has shown a meager skepticism towards vaccines compared to other countries), we have reached 70% of our vaccinated population much earlier than other countries and much earlier than seemed possible in early winter.