Is Lombardy close to herd immunity?

“Yesterday there were over 103 thousand administrations carried out in Lombardy. We are rapidly approaching 70% of the vaccinated population. A percentage that would mean the achievement of community immunity”. This is what the vice president and councilor for Welfare of the Lombardy Region, Letizia Moratti, announced yesterday on Facebook, thus hoping to close the game with Covid in a very short time. It’s really like this? In reality, looking at the data, Moratti could have been a little more cautious.

At the moment, Lombardy has in fact carried out 4,350,715 first doses and 2,077,019 recalls. Which means a percentage of people vaccinated with the first dose of less than 45%, while totally immunized people are less than 25%, according to data from the Ministry of Health which probably also includes those vaccinated with the single-dose J&J. 66.8% of administrations took place with the Pfizer-BioNTech vaccine, 20.85% with AstraZeneca and for the remainder with Moderna (9.32) and Janssen (3.03).

Even considering the fact that mRNA vaccines are particularly effective and according to many studies they are able to prevent infection in most cases, herd immunity does not seem to be one step away. Moreover, as clearly emerges from the graphs published by the Gimbe foundation (updated to 4 June), Lombardy is just above the average as a percentage of the vaccinated population.

How far away is herd immunity

The fact remains that after a slow start, the Region has gotten into gear and that over 100 thousand administrations a day are a remarkable result. How far away is community immunity then? Most experts place the bar around 70-80% of the vaccinated population, but it is by no means certain that the coronavirus will be completely crushed. For the virologist Fabrizio Preglisco it is more likely that “in real practice with this type of disease” we will arrive “at an increasingly civilized containment and coexistence with the virus”, while Guido Silvestri, professor at Emory University in Atlanta, said recent that it would be “dangerous” at this moment “to think that vaccines already work in giving herd immunity” against Covid-19, “when the percentages of vaccinated people are still relatively low, like the current ones”. This is “really the sticking point”. “This attitude – he explained on Facebook, in a post on what he calls” deniers “of the seasonality of the pandemic coronavirus – would lead to relaxing the vaccination campaign, when instead we have to push everyone to vaccinate like crazy, from now until October” precisely for to reach that 70-80% of vaccinated people, “which will really allow to stop the spread of Sars-CoV-2”.

The unknown of the Delta variant

Finally, there is another unknown factor to be taken into account: the Delta (or Indian) variant which, although it is scarcely present today in Italy, has quickly become dominant in the United Kingdom, ousting the Kent mutation (B.1.1.7 or Alpha ) which in itself was much more contagious than the Wuhan strain. In addition to being more virulent (according to the first studies conducted in the UK it would also be associated with a risk of hospitalization up to 2.6 times higher than Alpha) this variant also proved to be more resistant to the first dose of vaccines. In particular, the decrease in preventing symptomatic disease would be 15-20%. The good news is that with the second dose the protection is still very high. In other words, with such a dangerous variant it perhaps makes little sense to speak of herd immunity based only on the number of the first doses. In Italy to date the percentage of totally immunized people is equal to 23.78% of the population over 12 years of age. There is still a long way to go.

(Top graph Gimbe Foundation)

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