Early Wednesday, I sat in an exam room, waiting with great anticipation for the “unblinding” — the part of the clinical trial where I’d find out whether I received the covid-19 vaccine or the placebo.

I had been waiting weeks for this moment. As a participant in the Johnson & Johnson study, I was told that soon after the vaccine was authorized by the Food and Drug Administration, participants’ “veils” would be lifted. If we were in the placebo group, we could then get the vaccine.

The researcher asked me to sign some paperwork and verify that my health status hadn’t changed. Then she looked over my file. “Control group,” she said. “You actually received the placebo.”

That was not what I was expecting to hear.

In December, I wrote about why I decided to enroll in a vaccine trial. I was inspired by other volunteers, and in particular, people from minority backgrounds who wanted to encourage others to trust the thorough scientific process that goes into developing vaccines. By the time I enrolled, Pfizer and Moderna already had encouraging results from their covid-19 vaccines, but there was still a need for additional research. The world faces a massive shortage that can be addressed only by more vaccines, and different vaccines may have different advantages — especially, as we’re learning, in combating emerging variants.

Johnson & Johnson’s vaccine has the distinct advantage of being a one-dose inoculation. The FDA authorized the vaccine after verifying the outstanding results that a single shot of the vaccine was 86 percent efficacious at preventing severe disease in the United States, and 100 percent in achieving the endpoint that matters most — stopping hospitalizations and deaths. Importantly, one of the study sites was in South Africa, where the concerning B.1.351 variant was dominant. The vaccine still proved effective against this variant; no one who received the vaccine in South Africa was hospitalized or died.

The arm of the trial I enrolled in looked to see whether two doses of the vaccine would give even better and longer-lasting protection than the one dose. During my initial visit, I answered questions on my medical history and exposure risk. I had my blood drawn and a nasal swab to look for antibodies and whether I already had the coronavirus. Then I received my first shot.

I was instructed to go about my daily activities, including mask-wearing and continued physical distancing. The point was not to deliberately expose participants to the coronavirus — this wasn’t necessary, because there was (and still is) so much coronavirus circulating in the community. Twice a week, I filled out a symptom questionnaire online. I also received home monitoring equipment to take my temperature and measure my oxygen level from time to time, as well as nasal swabs to test for the coronavirus if I developed symptoms. Sixty days later, I came back to the clinic for a second shot, then 14 days after that, my blood was drawn again to check for antibodies.

When the one-dose vaccine was authorized in February, I knew that it was only a matter of time before the study participants would be unblinded. The company had announced it would do this, and in any case, it was the best practice ethically — when there’s a deadly disease for which there’s now a vaccine available, people who received the placebo should be told that. I definitely wanted to find out, though I thought I already knew the result: I had a high-risk coronavirus exposure where others around me tested positive and I didn’t. I was pretty convinced that I’d received the vaccine.

So it was a bit of a shock when I heard that I’d received the placebo. My surprise quickly turned to gratitude. I was grateful that the study site immediately gave me the shot, this time of the actual vaccine. I experienced no side effects, and now I know I will be well-protected from covid-19 and can soon resume many pre-pandemic activities. But my vaccine trial journey is not over. Now, I’m officially in the one-dose arm of the trial, where my results will be compared with those who received two doses of the vaccine. For the next two years, I’ll still be completing twice-weekly symptom checks and getting occasional blood draws and nasal swabs.

But most of all, I’m proud, because I’m part of the effort that’s helping to end this deadly pandemic. Of course, it’s the scientists who developed the vaccines who should take a bow when it comes to this remarkable medical achievement — but a successful scientific process has many authors, including the tens of thousands of volunteers who chose to take part in each study.

No matter whether we received a placebo or a vaccine, we are instrumental to the meticulous and rigorous science that has delivered, at a moment of great global peril, vaccines that are safe, effective and life-saving.

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