Can we Lyft (or Uber) our way to vaccination goals?

A new "megastudy" of 3.6 million patients looks at the impact of removing transportation barriers to getting important vaccinations

Vaccines are one of the most important and successful tools available for public health. They’re the reason many diseases are a thing of the past in the U.S., and over the years, they have saved millions from severe illness, hospitalization, and death from infectious diseases.

Of course, the protection that vaccines offer to individuals relies on them actually receiving the vaccine, and the protection vaccines offer to the larger population relies on a sufficient proportion of the population getting vaccinated.

Sometimes, we might get a recommended vaccine when we’re already at the doctor’s office for another reason - a fortuitous opportunity. But more often, when we get vaccinated, it’s not simply a matter of chance. Typically, we know or are told that we’re due for a vaccine, we remember to get one, and then we take the steps to do so, usually involving a time-consuming and sometimes costly trip to a doctor’s office or pharmacy. Each one of these - lack of knowledge, failure to keep track, time and cost - can create a barrier to vaccination. What can we do to reduce these barriers?

In a new “megastudy” of over 3.6 million Americans published in the journal Nature, researchers based at the University of Pennsylvania (including Katy Milkman and Angela Duckworth) and other institutions across the country collaborated with CVS Pharmacy to study ways to increase uptake of the updated COVID-19 booster in late 2022—when uptake of the recommended booster vaccine was quite low at only 11%.

One intervention they thought might help increase uptake? A free ride to and from the pharmacy.

Source: Adobe Stock

The Megastudy

Using records from CVS, the researchers identified adults who had previously received the initial COVID-19 vaccination series but who had not yet received the bivalent booster recommended by the CDC. They ultimately randomized 3.6 million patients in 65 different U.S. metropolitan areas into one of 9 different intervention groups, with a plan to measure what percentage of them got vaccinated at a CVS in the next 30 days.

The groups comprised:

• 7 text message-based reminder groups

• 1 group that was offered text reminders and free Lyft rides to and from a local CVS location

• 1 control group without any intervention.

The authors write:

We worked with CVS Pharmacy and a team of nine behavioural science experts to develop eight different intervention messages that were sent to patients by text message in early November 2022 to encourage adoption of the bivalent COVID-19 booster. All eight interventions consisted of an initial set of reminder texts with a follow-up set of reminder texts sent 7 days later, and all the tested text message reminders conveyed to patients that a vaccine was ‘recommended’ and ‘waiting for you’, language that was built on past research. The intervention of focal interest was designed to test the value of free round-trip rides to vaccination sites and it included the aforementioned standard reminder language but also provided people with one free round-trip ride by Lyft (a popular ride-sharing app) to and from a CVS Pharmacy in the month ahead.

Our seven other interventions did not offer free round-trip Lyft rides to a CVS Pharmacy. These interventions instead layered a range of different strategies for encouraging immunization on top of the standard reminder, from conveying current (high) rates of infection in a patient’s county to providing resources to combat misinformation.

Here’s an example series of text messages sent to about 492,000 patients randomized to the “CDC recommended” text-message intervention (all of the text-message interventions can be found here). On day 1 of the study, which was November 3, 2022, they sent this text message:

CVS Pharmacy: Hi [Patient First Name]! The CDC recommends updated COVID boosters to help prevent infection & severe illness. Your booster is waiting for you at CVS. Schedule: [link]

A week later, they sent the following text message:

CVS Pharmacy: Remember, a COVID booster is recommended by the CDC & waiting for you at CVS. Schedule: [link]

For the 50,000 patients who were randomized to getting a free ride, they were sent a similar text message that also included a link with a discount code that would open the Lyft app and provide them with a “Lyft Pass” to bring them to and from a nearby CVS location for free. Here’s what it would look like for a hypothetical patient in San Francisco:

Source: Milkman, K.L., Ellis, S.F., Gromet, D.M. et al. Megastudy shows that reminders boost vaccination but adding free rides does not. Nature (2024).

What did the study find?

To best understand the results, let’s start with the control group, who were due for a booster but didn’t get any reminders or free rides. Of these 492,000 patients, about 5% of them got their booster at a CVS over the 30-day study period.

Next, let’s look at the patients who got the various text message reminders but weren’t offered a free ride—about 3.1 million of them in total. Across the various types of text messages and reminders, 6.0-6.3% of them ended up getting vaccinated at a CVS in the next 30 days—a modest, but significant increase over the control group.

Among the 50,000 people offered a free ride (as part of a text reminder), 6.1% of them ended up getting vaccinated at CVS in the next 30 days—no more than the patients who only received a text-message reminder—suggesting that the free Lyft to a CVS didn’t actually lead to more vaccinations above and beyond what was achieved by text messages alone.

Source: Milkman, K.L., Ellis, S.F., Gromet, D.M. et al. Megastudy shows that reminders boost vaccination but adding free rides does not. Nature (2024).

Why didn’t a free Lyft increase vaccinations?

This study offered pretty convincing evidence that text-message reminders could modestly increase vaccination rates (a finding consistent with prior research on the topic), but that an additional free ride to the vaccine didn’t make a difference. But impressive as this study was in its size, it doesn’t tell us exactly why the free ride didn’t make a difference.

Looking through the study’s supplemental data, we see that of the 50,000 patients offered a free ride to the vaccine, only 0.1% actually took one (just 50 people!)—and these rides were estimated to be worth about $20 per patient. And while some people may simply not be into ride share apps and/or not have the Lyft app on their phone, this is still a remarkably small number.

At the same time, there are so many CVS locations that in major metro areas, the closest CVS in any given location within a metro area was estimated to be less than a mile away, on average. This means that if CVS locations are purposefully located to be in convenient areas that people might pass in their daily lives—and presumably they are—a free ride just might not be needed for someone interested in getting a vaccine.

While there are many more fascinating details of this study, taken as a whole, it says to us that contrary to intuition, physical transportation to a vaccination site may just not be a meaningful barrier to COVID booster vaccination—at least among the patients in this study who had previously brought themselves to a CVS to get their initial COVID vaccine series.

It may be that for other populations—such as those who usually get vaccinated at their doctor’s office (which might be farther away), those who are less independently mobile, or those living in more rural areas—a free ride might make more of a difference.

The bigger picture

As we’re sure you’re well aware from our vantage point here in 2024, hitting vaccination goals to maximize public health can be quite challenging. There are many reasons for this that the World Health Organization classifies into three broad categories known as the “3 C’s”: factors of complacency (perceiving risks of the disease or the benefits of a vaccine to be low), confidence (lacking trust in the medical system and vaccine manufacturers), and convenience.

In our book Random Acts of Medicine (now available in paperback to bring to the beach this summer—we had to get the plug in!), we break down a study of ours that focused on that last factor of “convenience.” Our results suggested that the inconvenience of having to bring young children to an extra doctor’s appointment to get a flu shot substantially reduced the chances of their ever receiving one for a given flu season.

Now available in paperback!

But getting vaccinated is inconvenient for adults, too, and there are real costs to doing so. People may lose out on income if they take off work to get the vaccine, have travel expenses like gas or bus fare (a cost the Lyft megastudy tried to address), and for some, the vaccine itself may have a monetary cost as well (fortunately this is an increasingly uncommon occurrence).

But there are also the non-financial economic “costs” of vaccination: the time it takes to go to and return from the vaccination site, time spent waiting and filling out paperwork, pain from the injection itself, discomfort from known side effects from the vaccine (like fever or sore arm), to name a few. A free ride to and from the vaccination site doesn’t ameliorate any of these costs—and it certainly doesn’t address other vaccination barriers of complacency or confidence.

It’s really important, however, to do what these researchers did and actually investigate the various factors if our goal is to increase vaccination rates. Intuition would tell us that a text message reminder might help a little bit (it did) and free ride might help a lot (it didn't). As much as “megastudies” like this one can be highly informative, they’re probably too much of a Lyft (ahem) to study every aspect of vaccination behaviors—which means we’ll have to take advantage of all the data we can to better understand this complex topic.