| You have to learn something and forget it six times before it's permanently in your head, my French teacher told me. Immunity works in a similar way. The more our immune system sees a pathogen, the better and faster it is at recalling how to fight it. Waning antibody levels in some highly vaccinated populations such as Israel have prompted calls to offer Covid booster shots to blunt fresh waves of hospitalizations in the face of the delta variant. So far, third doses seem to be working.  Photographer: Allen J. Schaben/Los Angeles Times Photographer: Allen J. Schaben/Los Angeles Times In fully vaccinated, healthy adults, booster shots from Moderna as well as Pfizer and its partner BioNTech cause antibodies to rebound to peak levels, if not well beyond, says Shane Crotty, a virologist and professor at the La Jolla Institute for Immunology's Center for Infectious Disease and Vaccine Research in California. Those antibodies are also likely to be more durable and adept at fighting a wider range of SARS-CoV-2 strains. All that fits with what we know about the mechanics of immune memory generation—"that it's frequently taken three exposures to get that," Crotty says. The response to boosters is the good news. The bad news is that large swaths of people in low- and middle-income nations are yet to get a sniff of any vaccine. Dozens of countries have administered at least one dose per person. Yet, as of Aug. 19, West Africa has delivered 2.4 doses per 100 people. In East and Southern Africa, the figure stands at 4.8 doses per 100 people. Booster doses in the context of such inequity is like handing out extra life vests to people who already have them, while we're leaving other people to drown, says Mike Ryan, executive director of the World Health Organization's health emergencies program.—Jason Gale | 
⇉〖OpenLoad〗 2020 Superintelligence PelÃcula Completa En LÃnea released 2020. story: La vida de Carol Peters se trastorna cuando es selecci...
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