2 buoni (secondo me) articoli non specialistici sull'evoluzione di sars cov 2:
https://www.statnews.com/2021/08/20/viral-evolution-101-coronavirus/https://www.sciencemag.org/news/2021/08/new-sars-cov-2-variants-have-changed-pandemic-what-will-virus-do-nextdel secondo oltre alla lettura consiglio di guardare attentamente il plot in alto
del primo, che e' un po' lungo, isolo un passaggio (si parla dell'evoluzione del virus, enfasi mie):
How will all this change as more people are protected?
Because basically everyone on the planet was susceptible to Covid-19 at first, the fastest-spreading variant has been able to outrun others. But as the environment changes, the pressures that select for certain characteristics do as well. And instead of a sprinter like Delta, a bulldozer could eventually get the advantage.
Take Beta and Gamma. These variants, which respectively appeared in South Africa and Brazil, emerged in areas that had massive first waves. That's led to one hypothesis that the variants took off because they could circulate better among people who had previous infections. Viruses that didn't have those features couldn't find as many new cells to infect, and fell back.
Scientists can't say for sure that's what happened with Beta and Gamma — perhaps they were just more transmissible in other ways. But it still holds that variants that have some ability to get around the immune response will get the upper hand in populations with greater levels of protection. They might not be causing severe disease in people who are protected — whether from vaccination or past infection — but if they can cause infections in at least some of those people and transmit from there, their prevalence will increase over other variants that have a harder time causing infections in protected people. (This appears to be happening with Delta to an extent, given that it's now known that some vaccinated people transmit the variant.)
When populations have high levels of immunity, "it favors [variants] that have some sort of escape mutation that doesn't throw a monkey wrench in the transmission side of things," said Michael Worobey, a professor of evolutionary biology at the University of Arizona.
Now, you may be wondering: If that's the case, does that mean a population that's largely vaccinated will actually encourage the virus to evade protection?
Different forces are at play here. But one key factor is that by cutting how much the virus replicates — both through preventing infections and by shortening the infections that do occur — vaccines limit the likelihood of additional, more dangerous variants. People who are protected against the virus can act as evolutionary dead ends.
"The pressure is there, but the opportunity is not," said Jeremy Kamil, a virologist at Louisiana State University Health Shreveport. "The virus has to replicate in order to mutate, but each virus doesn't get many lottery tickets in a vaccinated person who's infected."Secondo me in questo passaggio c'e' il principale incentivo a vaccinarsi: piu' gente si vaccina con questo vaccino "leaky", piu' e' probabile che una persona *non vaccinata* prenda una forma grave di covid nonostante il fatto che probabilmente non si e' vaccinata perche' si ritiene a basso rischio. la probabilità' che emerga questa variante e' genericamente bassa ma stimarla e' impossibile, perche' in gioco ci sono troppe variabili di cui non si sa nulla (i vaccinati che si infettano non sono un campione random della popolazione dei vaccinati ma non e' evidente cosa li tiene assieme). quindi ora come ora non vaccinarsi implica correre un rischio che non puoi stimare. e' un atto di fede.
dire che un vaccinato corre meno rischio di finire in intensiva a mio avviso puo' non essere convincente perche' da' l'idea che il rischio per un nonvaccinato non cambi. invece non e' cosi'. se l'unico argomento da dare a chi non vuole vaccinarsi e' che il vaccino non ti manda in intensiva, meglio metterlo obbligatorio secondo me. (io per lavoro sono de facto obbligato.)
