New cases, hospitalizations and deaths are declining rapidly, and the supply of available vaccines is increasing.
The country can move well on the path to herd immunity, to the point where enough people are protected from a disease that cannot be spread by that population.
But it can take months to get there, and no one expects it to return to our lives overnight before the epidemic.
U.S. With almost a%% of the population fully vaccinated, more than 66 million shots have been administered, according to the latest federal data. Promises from manufacturers suggest that the US should have enough vaccine supplies to cover everyone by June. More than a quarter of the population after a previous infection may already have natural immunity – and that number may be higher than official calculations.
However, some new types threaten progress, leaving the potential briefness given by the vaccine and leaving some degree of natural immunity. Vaccination hesitation can also create some limitations.
Their answers have been edited for length and clarity below.
There is still a lot to learn about Covid-19. But if you have to put a number on it, what level of population protection is needed to reach the mob resistance against Covid-19?
Casadeval: I am in the 65-80% range. We all expect that this virus is no different from other viruses and we will reach a stage where a sufficient number of people are immune so that the virus can no longer jump. It reaches a point where there are too many hosts, so fewer that it can jump, which crashes the epidemic. The number of cases is a risk, and in a declining turn, we see that the number of people who can jump it is declining.
Less: Community immunity is constant. As more immunity develops, the disease becomes easier to control. Right now, location control measures – such as masking and limited capacity – offer little protection, contributing to a reduction in cases. But to get the magic number where you can skip most of those steps and not worry about a big outbreak – there will still be some – somewhere between two-thirds to 80%. But the immunity of the extra community offers real benefits even when it is on the threshold.
Malati Riviera: We really need to vaccinate at least 70% of the population. If there are no significant interruptions in production or delivery it seems likely by the end of the year.
Mehta: I have seen estimates as low as 65% and as low as 95%. What I really want is to make sure we get at least 75%.
Murray: Respiratory viruses are very seasonal, so the level of immunity required in summer is much lower than in winter. Covid is dramatically more seasonal than other respiratory viruses, but as we learned, it is still. I would give the summer bunch immunity threshold 65% and for the winter 85%.
Individuals with Covid-19 may have some natural immunity after infection. Can we count those people towards mob immunity?
Casadeval: Yes. The number of people with reinfection is very low. There have certainly been some cases, and they have been documented. But even though all these viruses are still circulating, people don’t get sick again, and for me it’s really encouraging.
Less: In the short term, over the next six months or so, I will count everyone who has been infected and most of those who have been vaccinated as immunosuppressants. There are some cases of refraction, but it is mostly in people who had a very mild disease at first infection.
Malati Riviera: No, herd immunity can only be discussed in the context of mass vaccination. I am on the more conservative side and very hesitant to claim that natural immunity is making a significant difference in this number.
Mehta: Maybe. U.S. There have been many, many infections, but they have spread over time. It is difficult to know exactly how many people have been infected, and it seems that some people lose their immunity some time after infection. The population should be protected by targeted vaccination.
Murray: I would usually say yes, but some of the evidence surrounding the variant first found in South Africa brings it into question. Also, anything we know about losing natural immunity is purely speculative.
The new variants threaten the level of potential protection in terms of vaccine effectiveness and possible reassessment. How does this threat cut into the progression of mob immunity?
Casadeval: Variation on the horizon is a big threat. They have the potential to derail things, but I feel the potential stress. We know the variants are out there, but there are still very few cases of documented rearrangements. What suggests to me is that the forms are not avoiding the immune defenses. The most encouraging thing for me is how fast that turn is coming down. It gives me hope that we will break the curve before the variables become a threat.
Less: There are some types that seem to be escaping immunity and changing the equation. In a fully susceptible population, the average person with native strain spreads the virus to three people, so you need to have two people immune to start reducing the spread. But with some types, the average person can spread the disease to about five people, so you will need an immune system of four people to cut the spread.
Malati Riviera: The conversation around the variables really needs to be around infection prevention. If we keep the transmission low, we can keep the variables low. As the vaccines are coming out, however, we are still wearing masks and continuing to study mitigation strategies, it is time to buy ourselves.
Mehta: We think vaccines will provide good immunity to most types there, but there are some – especially the first known variant in South Africa – that have the potential to come around and change our level of protection. That’s why it’s so important that we get vaccinated as quickly as possible. The faster we get protection at a higher level in our community, the less likely it is to spread and grow.
Murray: If those forms spread, there is not a very clear way for the immune system of the herd, and it is a very difficult business trying to predict how fast they will spread. But cases are coming down fast, maybe even more than we expected.
Some surveys still show a significant amount of vaccine hesitation. How will this affect the path of animal husbandry immunity?
Casadeval: The number of cases is threatening, and for many years this vaccine has depended on what the remedy is. The more cases you have, the more likely you are to replicate the virus and infect the person. If we go that way and crash the turn, the chances of a bad view are low.
Malati Riviera: Anti-Wax people are a loud minority. They don’t represent a large group of people in this country, and I don’t think they get a tremendous victory when it comes to things like mob immunity. In general, people understand the barrier to not getting vaccinated, but we have had a big win with the campaign to overcome this.
Mehta: It is really understandable why some people in our communities may feel hesitant about vaccinations. All we have to do is take good care of them and become role models, not only by sharing knowledge and vaccinating ourselves, but also by taking precautionary measures like practicing good hand hygiene by wearing a mask.
Murray: If we do not vaccinate up to 10% to 25% of the population it increases the immunity of the herd. Even if the fear is not as bad as we think it is, it is still getting very close and vaccinating at the tipping point will make a big difference.
What is the bottom line? In general, when can we expect to return to normal?
Casadeval: No one in this world can tell you what percentage of security is needed or on what date. My gut is positive, and I think 2020 is going to be a better year than 2020. Assuming we don’t have the type that pushes the new lockdown, I think the latter half of this year will look different. If we can remove the restrictions in the fall, or if the rapid decline continues and the turn stays down a little earlier.
Less: When we get a very small number of new cases, it will be a sign that things can get better. As we take back control measures, we should do so slowly and deliberately and watch out for any resurgence. Some of these come down to determining what is common, as the fact of the matter is that we need to accept the fact that we will live with this virus forever. It will come again and again like the flu, but that doesn’t mean it will always be as volatile as it is now.
Malati Riviera: Vaccinating 0% of the population will be a complete game changer for us in terms of going back to what we could have done in the pre-coward days. I’m optimistic that this fall will look very different, and hopefully this means things like travel and socializing with mask-free loved ones. We are on our way to getting there if we keep trends down.
Mehta: Thanksgiving is my favorite holiday, when everyone in the family comes to my mother’s house. My hope – both personally and professionally – is that it happens before Thanksgiving.
Murray: I think it will be a quiet summer. But whether he will return is an open question, the answer to which we may not know until December. The two powerful powers – the seasonal and the standard of vaccination – will constantly bring things down, but we will have to wait.
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