On Friday, President Donald Trump announced "Operation Warp Speed," a partnership between the government and pharmaceutical companies to develop, manufacture and distribute hundreds of millions of doses of a COVID-19 vaccine by the end of 2020. Comparing the effort to the Manhattan Project that produced the atomic bomb, Trump acknowledged that the plan would be "risky and expensive."

And while the timing may offer hope to those tired of social distancing and help his re-election campaign, the timeline for Operation Warp Speed is likely unrealistically ambitious. There are even questions about the scientific feasibility of making an effective vaccine — not just this year, but in the near future.

While on Monday biotech company Moderna reported promising results from early human trials for one potential coronavirus vaccine, we shouldn't lose sight of the fact that there are miles to go before we have millions of doses of an effective vaccine. The history of large-scale, international efforts to develop and distribute vaccines has produced mixed results. Some, like the polio vaccine and the eradication of smallpox, were quite successful. Many others, despite decades of scientific focus and billions of dollars in investment, were not.

These failures — as well as the relative success of low-tech prevention strategies and drugs that treat virus patients — show the advantages of fighting the pandemic in a balanced way, one that combines the quest to develop a vaccine with efforts more likely to pay off.

Scientists have been trying to make a vaccine for malaria since the late 1960s. Pharmaceutical giant GlaxoSmithKline has had one candidate in development since 1984, known as RTS,S, that it developed in collaboration with the Walter Reed Army Institute of Research. The research program got a boost in 1999, when the Bill and Melinda Gates Foundation launched the Malaria Vaccine Initiative with a $50 million grant.

Managed by PATH, a Seattle-based global health nonprofit, the Malaria Vaccine Initiative has partnered with GlaxoSmithKline since 2001 to refine the RTS,S vaccine. Yet, despite this costly push that brought together public and private resources, more than 30 years since its initial development, the vaccine is still less than 40% effective and efficacy has been shown to wane over time.

While many scientists remain optimistic about the prospects of an eventual malaria vaccine, there are many challenges. There are four different species of malaria, each with several different genetic strains. In addition, the malaria parasite goes through distinct life-cycle stages in the course of infecting the human body and reproducing in the bloodstream, so any vaccine would need to be able to target multiple stages of the parasite's reproduction. This complexity spotlights why vaccines can be so hard to develop — even when there is real urgency and a significant commitment of resources.

Indeed, malaria remains one of the leading causes of death globally, where it is endemic in many low-income countries despite large-scale eradication efforts throughout the 20th century and the availability of low-tech, but effective, preventive measures like insecticide-treated bed nets that reach too few at-risk people thanks to a lack of resources and long-term community engagement.

It is a similar story with another major global killer, HIV/AIDS, where enormous effort has gone into producing a vaccine over the last 35 years without success. In 1984, when the Human Immunodeficiency Virus was identified as the cause of AIDS, Health and Human Services Secretary Margaret Heckler asserted that a vaccine would be ready for clinical trials within two years. In 1997, President Clinton likewise set a national scientific goal of developing an HIV vaccine within 10 years, and upped the NIH budget to create the Vaccine Research Center.

Yet, success has proved elusive. More than 30 vaccine candidates have been through clinical trials at more than 25 sites around the world since 1987 at an estimated cost of $500 million per year, but to this day none has been shown to be effective.

Yet antiretroviral drugs to treat HIV/AIDS have been available since 1987, and as a result of their effectiveness, contracting the virus is no longer a death sentence. In 2012, the Food and Drug Administration also approved a daily pill for those at high risk of contracting HIV, known as Pre-Exposure Prophylaxis, which prevents HIV infection.

Where they are available and made affordable, these drugs, as well as a low-tech solution — condom use — have proved effective at reducing the spread of HIV/AIDS, even without a vaccine. But access and affordability have been major barriers, especially in sub-Saharan Africa, leaving millions exposed to the horrors of HIV/AIDS.

Like the effort to develop malaria and HIV vaccines, the boldly titled Operation Warp Speed envisions a public-private partnership between various government agencies, and private pharmaceutical firms. It will be led by former GlaxoSmithKline executive Moncef Slaoui, and four-star general in charge of U.S. Army logistics Gustave Perna.

Historically, such partnerships have sought to produce affordable drugs and vaccines with very small profit margins for the private manufacturer. However, it is unclear whether Trump intends to control the price of a potential COVID-19 vaccine.

Operation Warp Speed comes on top of the Gates Foundation's own $125 million COVID-19 Therapeutics Accelerator, which is trying to bring together the World Health Organization, national governments and private industry, citing lessons learned from the 2014 Ebola epidemic in West Africa.

But as the bold proclamations and subsequent failures around malaria and HIV/AIDS demonstrate, global public health has historically suffered from its overconfidence in technological solutions. The relative success of other measures, like insecticide-treated bed nets to fight malaria, condoms to reduce the spread of HIV/AIDS and drugs to treat it, suggests that investing in a multipronged approach to treatment and prevention will be the best course of action. Too often, while resources have poured into innovative vaccine developments, insufficient funds — and political will — have existed to get these more simple solutions to people needing them the most.

These examples illustrate how a singular focus on developing a COVID-19 vaccine may divert funding away from more robust public health infrastructure and the testing and contact-tracing methods that have long been proven to curb epidemics. Investing in public health infrastructure can help ensure widespread accessibility if and when a vaccine is available. In the meantime, such investment can also help to guarantee that doctors and nurses have access to basic drugs and medical supplies, and that we have sufficient testing and contract-tracing capacity to mitigate the virus's spread as states start to reopen.

Heidi Morefield is a historian of medicine and technology and is a postdoctoral research associate in the global health program at Princeton University. She wrote this for the Washington Post.