If it weren’t so damn serious, it would be funny. In early December, Stephen Colbert riffed on the travel bans inflicted on South Africa and neighboring nations after the South Africans alerted the world to the emergence of a new variant of SARS-CoV-2: “We’re all lucky that South Africa alerted us to the dangers of Omicron. Thanks to them, the White House has issued a ban on travel from eight countries in southern Africa. Well, that’s good: You’ve got to contain the virus. So far, it’s only been found in the southern African countries of Austria, Belgium, Canada, Czech Republic, Denmark, France, Germany, Hong Kong, Israel, Italy, Japan, Netherlands, Portugal, Spain, Sweden, and the United Kingdom.” Once again, our comedians are our truth-tellers.

The Biden administration’s travel ban, with its focus on a set of southern African countries, its exclusion of US citizens and permanent residents traveling back from the region, and its open door to the more than three dozen other countries with known cases, is little more than pandemic theater. Travel bans can slow—but not stop—the emergence of the virus in certain circumstances: where outbreaks are detected early and where the travel bans are tied to a set of broader public health interventions, as one study analyzing travel bans on China in early 2020 found. But even in the context of this extreme policy by Chinese health authorities and world leaders, the march of SARS-CoV-2 was impeded for only a few weeks—with drastic human and economic consequences that far outweighed any medical impact the bans themselves might have had.

Punishing South Africa and its neighbors could have other serious side effects. The early detection of variants is critical for public health responses—so if the reward for such transparency by South Africa is a travel ban, which inflicts deep economic pain, the incentive for other countries to step forward early with critical information evaporates. Tulio de Oliveira, a Brazilian–South Africa bioinformatician who was part of the team that identified Omicron, also warned that the travel ban has meant that supplies of the reagents and other scientific materials needed to continue the work in the country to characterize the variant were running out. “Today, I spent a big part of my day talking to genomic and biotech companies as soon we will run out of reagents as airplanes are not flying to South Africa!” he tweeted. “It will be ‘evil’ if we cannot answer the questions that the world needs about Omicron due to the travel ban!” Though President Biden said he would follow the science at the start of his term, and though he rolled out scientific leaders to defend the ban, the scientific justification for travel bans is contentious at best—and the World Health Organization has opposed them in this case.

While the origin of the Omicron variant will likely never be known, the best guess is that it emerged in the context of an immunocompromised host—that is, someone with a weakened immune system, in whom the virus could have established long-term residency, beating back the host’s own feeble immune response, then mutating in situ to escape control and clearance from the body. From this original source, the variant then jumped to a new host and then another and another before rising to a level in the population at which it was detectable by genomic surveillance, as was done by the South African scientists.

The African continent is home to more than 25 million people living with HIV, and while millions are on antiretroviral treatment, many still are not, which means that millions of people are immunocompromised, as HIV is allowed to ravage their immune systems day by day. This provides a perfect setting for SARS-CoV-2 to establish persistent infections, settle in, and evolve to evade the immune responses in each immunocompromised host.

The notion that we can erect a Fortress America to withstand SARS-CoV-2 based on travel bans and boosters at home is a deadly delusion. “Build that wall” doesn’t work for public health. While publications like The Economist have recently discounted the argument that the emergence of the Omicron variant supports a call for global vaccine equity, their logic is fatally flawed. If, as the editors say, the likely origin of variants is the pool of immunocompromised hosts, vaccination is part of the solution to slow the emergence of new strains. More vaccines equals less transmission and fewer chances for SARS-CoV-2 to settle down in regions with millions of people whose immune systems are crumbling under the onslaught of HIV.

Scaling up vaccinations around the world is both a moral and a public health imperative—as is the need to ensure that drugs to combat the virus reach those who need them as they are developed and don’t just sit on the shelves of American hospitals. It also means that the response to the AIDS pandemic, which was badly disrupted by Covid-19, needs to be ramped up again, both to prevent millions of needless deaths from a treatable disease like HIV and to cut off the supply of immunocompromised hosts, on which SARS-CoV-2 seems to depend, at least in part, in order to spawn new variants in this newest of pandemics.