Less than a day after South African researchers announced the discovery of a worrying new covid-19 variant, President Biden took swift action to restrict travel from eight southern African nations. This was a necessary move, but it’s not nearly enough to prevent the worst-case scenario: another virus surge that sets the United States back in our pandemic recovery.

There is a lot unknown about the omicron variant, including whether it’s more transmissible and therefore will displace the already highly contagious delta variant; whether it causes more severe disease; and whether its mutations render existing vaccines less effective. Banning travel from countries with high caseloads of omicron could slow its seeding into the United States. This buys time for scientists to find out how much danger omicron truly poses and for health officials to increase prevention efforts.

As they are now, though, the travel precautions are far too porous to achieve this desired outcome. For one thing, they do not apply to U.S. citizens and permanent residents. Americans must be able to return home, but we need to acknowledge that if they are coming from southern Africa, they are just as likely as non-residents to carry omicron.

The Biden administration should set up quarantine facilities and require returning Americans to isolate for at least five days and then get a repeat test. This is particularly important given the seemingly high rate of coronavirus positivity among travelers from southern Africa. Of the approximately 600 passengers on two flights from South Africa to the Netherlands who underwent mandatory testing upon arrival, 61 people tested positive for the coronavirus, with at least 13 found due to omicron.

The United States should also extend a broad quarantine and testing regimen to all international visitors. Already, omicron has been found in Britain, Israel, Australia and Canada. In Belgium, the variant was detected in a traveler who visited Turkey and Egypt but not southern Africa. The United States will miss many entry points if we are too narrowly focused on one part of the world. We should not repeat the mistake from early 2020 when travel was closed to China, only to see covid-19 take hold here via Europe.

Of course, there is a very real probability that omicron is already in the United States. Our best defense continues to be vaccines, aided by other mitigation measures, such as testing and masking. The Biden administration must do everything possible to ramp up these measures, which will reduce the spread of the dominant delta variant as well as curb potential transmission of omicron.

In a speech on Monday, Biden called on all adults to receive boosters. This is an important course correction from the administration’s earlier mixed messaging that resulted in many Americans viewing additional doses as a luxury that can be postponed rather than urgent and essential. Many scientists believe that additional antibodies from a recent booster will give the best chance at protecting against new variants. The White House should lead a coordinated effort with all doctors’ offices, pharmacies and state and local health departments to identify Americans who have not yet been boosted. Sooner rather than later, the federal government should change the definition of “fully vaccinated” to include the booster.

Now is the time to pull out all the stops when it comes to compelling the unvaccinated. That includes a long-overdue vaccine requirement for domestic air and interstate train travel. In addition, the Biden administration should redouble its efforts to make at-home testing available to all and urge states, locales and businesses to reimplement indoor mask mandates for the unvaccinated.

While the United States must first focus on keeping its own residents safe, we and other wealthy countries have an obligation to assist the countries most affected by the travel bans. Many advocates have pointed to global vaccine inequity as the cause of omicron’s emergence, but a knee-jerk reaction to flood southern African nations with vaccines is not the answer. South Africa has such a surplus of vaccines that it asked Pfizer and Johnson & Johnson to stop sending more. Four other nations have requested for Pfizer to slow or stop shipping vaccines. The reasons for excess supply include disinformation resulting in low demand as well as lack of storage and distribution infrastructure. Helping southern Africa will require a nuanced approach that addresses each country’s specific circumstances.

We won’t know for weeks whether omicron is a false alarm. Even if it is, taking proactive measures could help prevent the United States from following Europe’s alarming coronavirus trajectory. The Biden administration was right to take the dramatic and difficult step of re-instituting travel restrictions, and administration officials need to do even more. They must assume the worst and deploy the tools we already have to prevent this new variant from threatening the tremendous progress made against covid-19.