Pfizer's shots are just one-tenth its adult dose. Pfizer and partner BioNTech found that two shots didn't provide enough protection in testing, so a third was added during the omicron wave. Pfizer's submitted data found no safety concerns and suggested that three shots were 80% effective in preventing symptomatic coronavirus infections. But that was based on just 10 COVID-19 cases; the calculation could change as more cases occur in the company's ongoing studies.