California may not achieve herd immunity for years. But vaccines will make the coronavirus more manageable

Between the emergence of new coronavirus variants, unreliable vaccine stocks, and unequal access to available doses, it can take months or even years longer than anyone would want to achieve herd immunity. It’s possible that California, the nation, and the world will never get there.

That would be a shame, but not necessarily disastrous. The available vaccines are very good at preventing serious diseases, even with the variants that appear to be somewhat resistant, and they can be adapted to the virus as it mutates. Vaccines will almost certainly reduce hospitalizations and deaths from COVID-19, and that could make the pandemic much more bearable in the coming months, long before it’s technically over.

“I am hopeful that by the beginning of the summer we will vaccinate the general public in a broader perspective. And we should see correspondingly wonderful results by early fall, ”said Dr. Catherine Blish, an infectious disease expert at Stanford.

Blish is still optimistic about the herd’s immunity, even if, like most of her peers, she has no idea how long it will take to get there. “The most important thing to remember is that we have to be patient,” she said.

Herd immunity occurs when enough of a population is immune to a virus that it can no longer spread. Measles is a case in point: Enough people in the United States have been vaccinated that the virus will only cause a problem when cases are brought in from other countries and happen to reach communities that are inadequately vaccinated, leading to local outbreaks.

It is not clear exactly how many people need to be vaccinated to achieve herd immunity with the coronavirus; Dr. Anthony Fauci, the country’s leading infectious disease expert, estimates 70% to 85%. But it’s a moving target based on how protective vaccines are against new variants and other factors, including the effectiveness of the vaccines in children and how long immunity lasts. Children are unlikely to be eligible for an injection until early next year, but research has shown that they are not causing the pandemic.

Regardless of what the final rate is, and assuming the vaccine supply becomes more reliable, many parts of the US can get close to herd immunity in six to eight months.

Along the way, counties should see a continuous, notable drop in hospitalizations and deaths. Some experts believe the vaccines are already helping, with fewer outbreaks in nursing homes in particular. The effects should become more apparent in the coming month as counties continue to reopen the economy and hospital admissions don’t rise again – although there is a risk of a new wave in cases where more contagious variants take hold, public health officials warn.

Once communities achieve immunity to herds, new cases should fall quickly. If the Bay Area were an island, after vaccinating about 80% to 90% of the residents, the pandemic could be over in two weeks, said Dr. George Rutherford, a UCSF infectious disease expert.

But global ties mean that even after the region or state, or even country, reaches the herd’s immunity level, the coronavirus will remain a threat – but a less life-altering one. If communities can reduce the number of cases to just a handful a day, they can quickly isolate and lock in new infections that are imported and prevent outbreaks.

“How would we live if there were 10 or 20 cases per day or even 100 cases per day in the United States? We would enjoy life considerably, ”said Dr. John Swartzberg, an infectious disease expert at UC Berkeley. The US currently reports more than 50,000 cases per day. “That’s what we can achieve with herd immunity.”

Assuming herd immunity is achievable, there are several variables that can slow it down. An unknown is how long immunity lasts after people are vaccinated. Some infectious disease experts fear that immunity could wane within a few months, which would mean the first round of people to be vaccinated would need boosters before the final groups receive a single dose. But most experts believe that immunity probably lasts longer than that, maybe years.

Variants can complicate things and can even make herd immunity an impossible target if the virus mutates too quickly to keep up with vaccines. But even then, the vaccines would likely prevent the most serious illnesses, and the coronavirus could become similar to influenza in terms of its impact on daily life and impact on healthcare.

The most worrying variants to date have come from South Africa and Brazil, both of which have been identified in small numbers in the United States; two cases of the variant from South Africa have been found in the Bay Area. Those variants decrease the effectiveness of vaccines, and they may also be able to bypass the natural immunity of a previous infection. That may mean that more people need to be vaccinated or need boosters for the population to achieve herd immunity.

“The current vaccines will still make a dent. They may not necessarily be able to tout the 95% effectiveness, ”said Shannon Bennett, chief of science at the California Academy of Sciences. “But I would take 60% in the blink of an eye.”