A health official administers a polio vaccine in 2014 in Nigeria, one of the few countries in the world where the wild polio virus remains endemic. (Sunday Alamba/Associated Press)

While December may be better known for religious holidays, the month is also home to two “global health” holidays. On Dec. 1, the world celebrates World AIDS Day. Since 1988, this has been a day to remember the more than 35 million people who have died of AIDS-related illnesses, and support those living with HIV.

And on Dec. 12, the world celebrates a newer holiday — Universal Health Coverage Day — which takes place on the anniversary of the U.N. General Assembly’s historic (and unanimous) 2012 endorsement of universal health coverage. The U.N. holiday calls attention to the growing global movement for universal health coverage, a goal the U.N. hopes to see the world achieve by 2030.

The road to AIDS care and health-care reforms were quite similar.

The two days may seem unrelated beyond a broad global health connection. But the movements that led to important reforms in treatment for AIDS and universal health care in some countries were remarkably similar. The political dynamics in each case were quite different, leading to vastly different outcomes.

In my recent book, “Achieving Access: Professional Movements and the Politics of Health Universalism,” I explore pioneering universal health care and AIDS treatment programs in Thailand and Brazil, as well as the health-care struggles in South Africa.

The book was animated by two simple questions: How and why do resource-constrained countries make costly commitments to universal health care and AIDS treatment? And how are we to make sense of the political dynamics that led to surprising health-care reforms in Thailand and Brazil but delays and disappointment in South Africa?

The research involved over 120 interviews with key informants in Thailand — with a universal health-care program many consider to be a model for the industrializing world — and 25 interviews in South Africa. I relied on the substantial body of existing literature on the reforms in Brazil.

Thailand, Brazil and South Africa share similarities that made them ripe for comparison. All three were transitioning from dictatorship: In Thailand, following a short-lived coup in 1991 and, before that, a longer period of rule by military leaders; in Brazil, under military rule from 1964 to 1985; and South Africa, following the end of apartheid in 1994. There were other similarities, including competing policy priorities at the time of transition, high levels of inequality and increasingly visible AIDS epidemics.

At the same time, each country’s decision to pursue health-care reforms was unexpected, given a number of factors: Health care and medicines are expensive, and costs are rising; caring for those with HIV/AIDS added stress to government budgets; the prevailing economic climate encouraged spending constraint, rather than expansion; and medical expertise was scarce. Two of the three countries also grappled with economic crisis. These factors made reform seem improbable, if not impossible.

What inspired these movements?

Conventional wisdom in political science and sociology is that democratization empowers the masses. At times of political transition, when dictators relinquish control and newly formed political parties are hungry to win votes, the masses give voice to new concerns, and these issues show up on political agendas.

Yet, in line with recent work that has shown how major new social programs in developing countries do not always reflect the priorities of citizens, my research highlights that the impetus for reform may actually be less broad-based than we might expect. While traditional activism was important, I found that democratization also empowered well-situated elites from esteemed professions, who in turn drew on their privileged positions in the state, their knowledge and their social networks, to outmaneuver the broader professions of which they are a part and deliver benefits to those who needed them.

In the domain of universal health care, where physicians dominate, these “professional movements” were composed of doctors, like Thailand’s Rural Doctors’ Movement. In the domain of AIDS treatment, which lies at the intersection of human rights and intellectual property law, legal movements of lawyers and activist health professionals with expertise in the law were particularly important. Use of the law to advance reform was a core element of the identity of movement organizations like South Africa’s AIDS Law Project (now known as Section 27).

In the United States, we typically think of medical associations, like the American Medical Association, as powerful and entrenched. Historical accounts have pointed to the role that the AMA has played in stymieing some major reforms, like national health insurance, in the United States.

Professional movements promoted these reforms heavily.

To counter their influence, professional movements used cunning strategies to institutionalize universal health care that included embedding strategic principles and provisions in new constitutions; financing and mobilizing national petition campaigns; convening panels of experts to increase reform legitimacy and visibility; convincing political parties to take up universal coverage; drafting bills within the ministry; creating implementation strategies to deliver benefits to the masses, even before parliamentary debates began; and using allies to resist political opponents.

While professional movements promoted reforms that aimed to expand access to health care and lifesaving treatment for AIDS, they confronted very different political dynamics in Thailand and Brazil than in South Africa. Political competition following democratic transition in Thailand and Brazil was fierce, while in South Africa the African National Congress had few challengers. In 1999, for example, the ANC won 66 percent of the vote, while the second-place Democratic Alliance claimed just 9.6 percent.

Although we often think of winning a sizable vote share as providing parties with a strong mandate to move forward with policy, these different political dynamics help explain why political parties proved more open to professional movement entreaties and strategies in Thailand and Brazil — and why National Health Insurance reforms stalled and HIV/AIDS policy (for a time) rolled backward in South Africa. While the deep legacies wrought by apartheid magnified the challenges of reform, the ANC’s unrivaled popularity meant the party could afford to resist campaigns by professional movements in South Africa.

The result is that the ANC expanded access to health care incrementally in the 1990s and established an AIDS treatment program only after great struggle. The broader dream of opening the doors of the country’s private clinics and hospitals to millions has remained elusive. Although South Africa is now considering a national health insurance bill, questions remain about its viability, nearly 25 years after apartheid fell.

To be sure, no health reform is perfect, and the reforms in Thailand and Brazil have faced strong challenges since they were adopted. But as other nations consider their own health-care reforms, they can learn from the experiences of countries that managed to put in place remarkable reforms, despite the odds.

Joseph Harris is an assistant professor of sociology at Boston University.