Tuesday, October 19

Experts argue that herd immunity will need to increase beyond 70%


A nurse holds up a Covid-19 vaccine (FILE)

A nurse holds up a Covid-19 vaccine (FILE)
Alberto Ortega – Europa Press

In any cycling race, the one who goes in the middle of the peloton, surrounded by other runners, has the protection of the rest of his companions with respect to the wind so his pedaling has less resistance and, therefore, is simpler, uses less energy and has more strength for difficult moments on the road. The so-called group immunity has a similar effect: living among vaccinated makes it difficult for the virus to pass, which is weakened by the immunization firewall, preventing it from reaching those who are not vaccinated. That, at least, is the theory.

The Valencian Community advances in vaccination against covid. This week the inoculation among twentysomethings began in a massive way and there are already more than 70% of the population to be vaccinated (the 4.5 million Valencians and Valencians over 12 years old) who have a dose. In this case, 70% is not just any number, it is the threshold that was set to reach the so-called herd immunity from which the COVID pandemic would begin to remit. Goal accomplished then? Not yet.

“Group immunity is a calculation, but it is not a fixed number that marks the end of the pandemic, it does not mean that when going from 69% to 70% of vaccinated, the transmission ends”, explains Salvador Peiró, Public Health specialist of the Fisabio Foundation. As detailed, these first accounts were made from the idea of ​​an effectiveness 100% of vaccines, that the vaccinated were not contagious and that the reproduction index of the virus was three: each infected transmitted the virus to three other people.

The summer wave of covid the conception of group immunity has changed and it has forced to redo the operations after the evidence that its evolution has left behind. As Peiró explains, the vaccines do not have a total effectiveness but are between 80 and 90% depending on the variant, those immunized not only can be infected but also transmit the virus and, in addition, this rebound has caused the Delta mutation and its greater expansion capacity is the predominant one, which has made the reproduction rate rise and that each infected person passes the virus to more people.

With all this, the epidemiologist ensures that the calculation of group immunity should exceed the 70% mentioned and places it at around 80 and 85%, yes, “over the entire population.” “This would include children under 12 years of age in the calculation,” he says, a population for which a decision has not yet been made regarding whether or not they should receive the anticovid injection. To vaccinate them or not will influence the percentages that are necessary among adults (also between 12 and 18 years old) to reach group immunity.

For now the specialists do not fear that those reluctant to inoculation are the that prevent reaching that global protection.


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