Herd Immunity means enough people are vaccinated so the community is protected against an illness or virus. Those who have had Covid-19, plus those who have been vaccinated become part of the herd.
Depending on who you listen to, herd immunity is reached when between 60-90% of the population has become vaccinated. While there are a number of us who are unwilling to become vaccinated, as long as most people are exposed either naturally or through inoculation, we can crowd out the virus.
There is also the concern of viral variants, some of which may be less affected by the current vaccination campaigns. The scientific community believes the speed we vaccinate the population will determine our effectiveness as it reduced the number of future viral variants. The idea is that the sooner Covid-19 is neutralized, the fewer future variants will be a problem for society.
Covid-19 vaccines seem to be very effective in developing an immune response. Even after the first inoculation, societal numbers of infections have been reduced. Variants may pose a problem since the vaccines may not be as effective on certain variants.
In a given year, the flu vaccine may be 38% effective. With a variant, a 90+ effective vaccine may only be 50+ effective depending on the variant. This is still more effective than a flu vaccine.
What percentage of effectiveness is good enough? Can we ever reach herd immunity to Covid-19 or will we be constantly dealing with new and less harmful variants in a similar way we do with the Flu vaccine?
These questions and more are covered in this recent article that was published in the Atlantic. Check it out
What If We Never Reach Herd Immunity?
Hitting the threshold might actually be impossible. But vaccines can still help end the pandemic.
SARAH ZHANG FEBRUARY 9, 2021
Let’s begin by defining our terms. Herd immunity is the hazy, long-promised end of the pandemic, but its requirements are quite specific. Jennie Lavine, a biologist at Emory University, likens it to wet logs in a campfire. If there’s enough water in the logs—if there’s enough immunity in a population—“you can’t get the fire to start, period,” she says. To be more technical about it, a population reaches herd immunity when the average number of people infected by a single sick person falls below one. Patient zero might infect another person, but that second person can’t infect a third. This is what happens with measles, polio, and several other diseases for which vaccines have achieved herd immunity in the United States. A case might land here, but the spark never finds much dry fuel. The outbreak never sustains itself.
For COVID-19, the herd-immunity threshold is estimated to be between 60 and 90 percent. That’s the proportion of people who need to have immunity either from vaccination or from prior infection. In the U.S., the countdown to when enough people are vaccinated to reach herd immunity has already begun.