That Vox article IMO is badly written, but here is an excerpt from another article with results from the UK:
'A group of researchers in the United Kingdom say they have seen early signs that Pfizer’s vaccines have contributed to a drop in health-care workers testing positive for the virus. Vaccinated health-care workers were 53% less likely to test positive for SARS-CoV-2 12 days after their first dose than were unvaccinated workers, says Tim Spector, a genetic epidemiologist at King’s College London, who presented the preliminary results in an online webinar on 3 February. The analysis was based on about 13,000 vaccinated people and about 33,000 unvaccinated people who reported their results using a mobile-phone app. “This is the first sign in real life, outside trials, what the effect is of a single dose,” he said."'
The country is the first to see a direct effect of vaccines working in such a large group of people.
www.nature.com
Here is another which cited a 33% reduction in positivity after 14 days following receiving a single dose.
Early data from Israel suggests Covid-19 infection rates began to decrease among a group of vaccine recipients two weeks after they received the first shot of the Pfizer-BioNTech vaccine, offering important insights to other countries as they roll out their own campaigns.
www.google.com