For more than a year since COVID-19 improved our lives, the concept of herd immunity has drifted into our future as the goal to achieve: Once enough of us have achieved immunity by recovering from COVID-19 or vaccination, can we put the pandemic in the rearview mirror and return to life as we knew it.
Experience with Spanish flu and measles has given us reason to believe that the virus will disappear as soon as it cannot find enough unprotected people to infect.
But even with the vaccination effort expanding this month to everyone 16 years and older, experts and authorities are returning from the idea that herd immunity is around the corner or even achievable. Not least among them is the Government of California, Gavin Newsom.
“I’m afraid it’s a bit of an illusion, this idea of herd immunity,” Newsom said Tuesday when asked if his government has a prediction for when California will reach its goal.
“You have people who are simply not going to take the vaccine,” Newsom explained. ‘If you want to achieve herd immunity, it must include all our children, and yet we do not have … permission in general for people under the age of 16. You should also be aware of some of the variants … combined with resistance. All that makes the question ‘very, very difficult to answer’.
Health experts mostly said that the governor is not of the point.
“This is a very nuanced issue,” says Dr. John Swartzberg, Professor Emeritus of Infectious Diseases and Vaccination at the UC Berkeley-UCSF Joint Medical Program. “I do not think the governor is off the wall, but I think it deserves a better explanation.”
Herd immunity boils down to a matter of math – the point where enough people have immunity to a disease to eradicate its spread. But a number of variables can drive the solution of the equation crazy. The more contagious the disease, the more people need to be immune to slow the spread.
Andrew Noymer, an epidemiologist and population health scientist at UC Irvine, noted that herd immunity is not the same as eradicating diseases, as with smallpox through a global vaccination campaign. With herd immunity, there will still be infections, even small outbreaks, as with measles. They just will not spread far.
Newsom said COVID-19 in 70%, 85% even 90% of the population needs immunity, and indicated that he does not have much confidence in a particular figure.
“It’s not a magic number – the governor seemed like it – it’s more of a conceptual idea,” Swartzberg said. ‘We want to get to the point where the chances of us being close to someone who is infected are very low. Once it gets to that point, the virus will very difficult to find a person in whom it can reproduce. If we have a very high degree of community immunity, it is very unlikely that this virus will be able to sustain itself in any way to have a strong impact on our lives. ‘
Experts from the University of Washington’s Institute for Health Metrics and Evaluation, who use a widely respected computer model for the projection of COVID-19 outbreaks, do not expect herd immunity in the US until next year.
Ali H. Mokdad, a professor of health metrics at the institute, estimates that 85% of the population will need immunity to the virus to establish herd immunity because it is so contagious. But only about 65% are likely to have immunity by winter, he said, because children under 16 are not currently eligible for the vaccine and many Americans do not want to take it. More contagious variants of the virus that can evade some of the protection of the vaccines contribute to this.
“We will achieve herd immunity, but not before this winter,” Mokdad said. He expects the virus to subside during the summer and fall, but to return in the winter with colder, drier weather that is more favorable for its spread. It is unlikely that it will bring about a resurgence as quickly as last winter, but it is likely that health officials will have to impose the travel and mask requirements and restrictions on the event.
Dr. Anthony Fauci, the country’s leading expert on infectious diseases, said during a Senate hearing last month that unvaccinated children impair the immunity of herds, saying: “We must be careful about using this concept of herd immunity. get married, because we really do not know exactly for this specific virus, what it is. ”
The unknowns make the projection of herd immunity difficult – how long will vaccines or immunity against past infections protect us and will they stop new virus mutations in the US and around the world that are finally coming here?
“Herd immunity is a gripping target, simply because we do not have enough vaccine to vaccinate the world,” Mokdad said.
Not all experts buy the pessimism due to herd immunity. Dr. Monica Gandhi, an epidemiologist at UC San Francisco, cites several reasons why it is reasonable to expect herd immunity in the near future.
The vaccines currently approved by Pfizer and Moderna in the United States are more effective than we would ever have hoped, preventing 100% of serious diseases in rollout studies and 95% of symptomatic infections, making it likely that our herd- will achieve immunity, ”Gandhi said.
She notes that studies from Israel, which led the world to vaccinate the population, have shown that children do not need to be vaccinated to reduce transmission, and that the infection of only those aged 16 years and older is significantly reduced .
Israel and the United Kingdom, which was also a world leader in vaccinating their people, saw very low transmission rates of the virus with vaccination levels of 60% and 48% respectively, even with the restriction of closure restrictions and more people meeting, said Gandhi. The vaccines have shown good protection against the known variants, she added, and Californians have shown that they are more receptive to the vaccines than in other states.
However, other experts advise not to place bets on when the herd immunity comes.
Epidemiologist Lauren Ancel Meyers, executive director of the University of Texas at Austin COVID-19 Modeling Consortium, said “it depends on the effectiveness and duration of the immunity obtained through infection or vaccination, whether we have a low immunity in our communities, and whether there are emerging variants that can evade immunity. ”
“Because COVID-19 is such a sneaky virus – it spreads quickly and quietly – it will only start to disappear before the vast majority of people are immunized,” Meyers said. “And we will not get to this point as long as there are people who have a low level of immunity.”
UC Irvine’s Noymer said we probably would not know when we reached herd immunity, but even then it could be temporary.
“A lot of people think this thing is just disappearing,” Noymer said. “Herd immunity is declining as well as waxing. I think we can achieve herd immunity, but that does not mean we are going to stay there. ”