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Crew immunity: How the United States could reach a normal post-pandemic with 60 partial vaccinations



When America’s Covid-19 vaccine development began last December, White House medical adviser Anthony Fauci said the coronavirus herd immunity threshold could be 80 to 90 percent. The implication was demoralizing: America needed to get as many as 90 percent of its people vaccinated to really stop the virus from spreading freely. With approx. 20 percent of the population still resistant to getting a vaccine, almost universal vaccination seems very unlikely – leading to a recent New York Times article suggesting that herd immunity may be impossible.

But recent data from Israel paints a more hopeful picture: With about 60 percent of the population vaccinated, Israel has managed to almost completely reopen its economy and crush the number of coronavirus cases and deaths to almost zero. The country still has some requirements in place ̵

1; especially indoor masking and vaccine passport requirements – but it is much closer to normal than it could afford to be, with no guarantee of safety, just months ago.

We still do not know for sure what the threshold for herd immunity is. Some experts said it could be as low as 60 percent. But Israel’s data suggest we could get our lives much closer to normal without worrying about the risk of fatal infection – with far less than 90 percent vaccination rates.

It’s a sign that there’s a pretty safe gray area – an endgame for Covid-19 of sorts – between lockdowns and pre-pandemic after a year of trying to find that balance in the US triggered wave after wave of Covid-19.

The best news for Americans: We’re not too far from getting 60 percent of the country vaccinated. Already, more than 40 percent of the population has received at least one dose, and more than 30 percent are fully vaccinated based on federal data. At current vaccination rates, the United States could hit 60 percent partial vaccination as soon as this month or June and 60 percent full vaccination in June or July – all within three months. Already, Covid-19 cases in the United States have fallen by about 27 percent in the last two weeks.

There’s still a lot we do not know. Hitting 60 percent possibly enables infection control without being true flock immunity when the virus can no longer circulate widely. Either way, it would help ensure that coronavirus does not come back again if one gets the vaccination rate higher than 60 percent – especially if variants, changes in weather and seasons or variation in vaccination rates depending on the condition can let the virus break through our defenses.

So until we know for sure that it is safe, it is a good idea to continue to be careful in some ways, including wearing masks and consider restricting some activities to vaccinated people.

Yet Israel shows that we may be able to resume our lives much closer to normal – enjoy everything from restaurants to live music and sports – long before we vaccinate 90 percent of the country (if we can even do so). As the biostatistician Natalie Dean from the University of Florida told me, Israel’s data say “good for what we can do in the United States. Maybe we can get really far away as 60 percent of people get vaccinated. ”

What Israel tells us about the inflection point

Compared to the rest of the world, Israel’s current experience may almost resemble another planet. Isabel Kershner wrote in the New York Times, explaining what normal Israelis are now in when they get “a taste of a post-pandemic future.” People eat out, go to packed concerts and attend sporting events – often without masking and with little or no physical distance.

Part of the story here is that Israel still has some precautions in place, especially masking and capacity requirements for indoor venues. The country has also embraced widespread use of “Green Passes”, where evidence of vaccination, previous Covid-19 infection or a negative coronavirus test becomes a ticket to some of the more risky activities, although enforcement is reportedly tainted.

But the big element seems to be Israel’s world-leading vaccination campaign. Israel had tried to reopen before, only to see some of the world’s biggest increases in coronavirus last summer and then winter.

When Israel moved to almost complete reopening in March, it still had many daily new Covid-19 cases – more than twice as many per. Inhabitant as the United States. But this time, nearly 60 percent of the population had received at least one vaccine dose (which provides at least some protection), and more than 40 percent were fully vaccinated. Thus, Israel’s affairs began to decline – more than 95 percent fell through today. Israel had almost completely reopened, but instead of the previous increases it saw in previous reopens, it saw a massive drop in cases.

Today, more than 60 percent of Israel’s population is fully vaccinated, and as the country remains open, Covid-19 deaths are reported every day in the individual digits and sometimes zero.

“The Israel data should make us feel optimistic and persuade people to take the shots,” said William Hanage, an epidemiologist at Harvard.

None of this means that Israel has definitely defeated Covid-19. The apparent inflection point – 60 percent of the country, at least partially vaccinated – could instead reflect the point at which “exponential decay” begins, as cases fall just as fast as previous rises. That does not mean that Covid-19 has been defeated and the virus can still come back, even regionally. But it’s the kind of decline in Covid-19 that almost everyone has been waiting for since the rollout of the vaccine began.

There are some other notable reservations. The biggest: Israel is not fully reopened. It is very likely that its current limitations, from mask mandates to vaccine passports, will keep matters suppressed – and things would be much worse without these interventions. Israel is not proof that a place can almost completely reopen by hitting 60 percent vaccination rates; it is proof that a place can be opened almost completely with the least intrusive precautions at vaccination rates of 60 percent.

It may be that Israel is too cautious and could fully reopen with none of these precautions at 60 percent vaccination rates, but we just do not know yet.

Another important consideration is natural immunity. In places that have seen large waves of Covid-19, including Israel and the United States, many people have built up immunity after recovering from infection. We do not know exactly the total number of people with natural immunity given the role of asymptomatic spread. Nor can we just add the previous number to the total number of vaccinated people because some previously infected people have received the vaccine (since vaccines provide more protection than natural immunity). But we know that natural immunity is another layer of population protection on top of the vaccine.

Other factors may also play a role. The number of daily new cases is important because more viruses out there make it much more likely that the pathogen is capable of jumping from host to host. Seasonality can also matter: If the weather is good and people are able to do things outdoors, it becomes much harder for the virus to spread as free air, heat and moisture weaken it.

What can really matter is vaccination of older adults. In particular, Israel has vaccinated 90 plus percent of the population 60 years and older. Given that people age 65 and older in the United States account for 80 percent of Covid-19 deaths, it may be vaccinating this group along with populations with comorbidities that matters most to the coronavirus endgame. It can even bring down reported cases, not just deaths and hospitalizations, as people are less likely to report asymptomatic or mild symptoms. (To that end, in the wake of this goal, more than 80 percent of the population 65 and over are now at least partially vaccinated.)

An important consideration is the massive state-by-state variation in vaccination rates. While 61 percent of the population of New Hampshire has received at least one shot, only 31 percent of the population of Mississippi has it. So just hitting 60 percent at the national level probably won’t be enough for every state to swing its doors back, at least for sure.

Even with these caveats, the news from Israel seems pretty good: There seems to be a sure way to get much closer at a vaccination rate of 60 percent – and the US is very close to reaching that point.

There are still good reasons to aim higher with vaccines

When I asked experts about all this, they repeatedly emphasized that we still do not know what the herd’s immunity threshold really is. Experts give different estimates: While Fauci estimated that the correct threshold is 80 to 90 percent, Baylor College of Medicine infectious disease expert Peter Hotez told me that his estimate of herd immunity is 60 to 75 percent.

Herd immunity can also be a moving target. “One of the challenges is that people hear [of population immunity] and think of it as a very static concept, ”said Jen Kates, Director of Global Health and HIV Policy at the Kaiser Family Foundation. However, this is not true given the effects that various interventions, weather and other variables can have on the rate of infection and therefore the level of immunity required to suppress infections. “It makes it difficult to say what the percentage is for the United States. It will vary by location. ”

Therefore, real world data is important. “The evidence was always in the number in what we actually observe in case of incidents,” Dean said. “Everything else was just speculation, estimate.”

At the same time, the uncertainty surrounding the bending point and the crew’s immunity should make us all a little wary of putting too much stock in Israel’s experience. There are also other good reasons to be vaccinated, from the selfish (a vaccine is the best guarantee we have as individuals against coronavirus) to the population level (more vaccination above a theoretical herd immunity limit, even more transmission stops).

“The hope is that we start to see declines when we start hitting around 60 percent,” Hotez said. “But I think in order to really bring it down to true containment and really stop transmission, we’re probably going to have to go higher than 65 percent.”

A major complication here is children, as there are still no Covid-19 vaccines approved for children under 16. If the goal is to vaccinate 60 percent of the population, but there is no vaccine for children, the goal is really to vaccinate at least 75 percent of adults, which is a bigger challenge. With 56 percent of adults receiving at least one dose, we are not there yet.

To that end, America still needs to do much more work to vaccinate people. The number of doses administered daily has fallen in recent weeks to approx. 2.4 million on average from a height of almost 3.4 million.

Experts attribute this to America’s vaccine rollout problem, shifting from supply to demand. Brown University School of Public Health Dean Ashish Jha used the analogy of a new iPhone coming out: So far, the United States has vaccinated the most enthusiastic, those willing to camp overnight against the vaccines. Now the United States needs to make it less difficult for the less enthusiastic to get the shot – make it easier to get a deal or remove the appointment requirements completely and bring vaccines closer to where people are, including their homes, workplaces, doctors’ offices, or even hot spots for socializing and entertainment.

The United States may also need to work with those who are truly resilient. Based on public polls, it is about 10 to 25 percent of American adults. We could hit 60 percent of Americans or even 75 percent of adults without them. But converting as many of these people as possible will still help us get there faster. This may require extensive messaging efforts, especially from Republican leaders whose voters are more likely to be hesitant.

If we do all this right, there is really good news: the end may not only be in sight, it may be even closer than we think.

“After going through this, people tend to go crazy,” Kates said. “[People] is like: ‘Is this true? Are we really okay? ‘The trauma is deep so there is a bit of anxiety about it. But I think we’re just a much better place than we were not long ago. ”


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