With COVID-19 shots from Pfizer-BioNTech and Moderna Inc. both available in Japan's booster campaign, many may be wondering how the two shots compare.

As the booster rollout speeds up, some are also wondering if they should stick with the same kind of shot they got in the first round or go with a cross-vaccination: two Pfizers and a Moderna, or two Modernas and a Pfizer.

For boosters, Japan plans to distribute significantly more doses from Moderna than from Pfizer — 58 million versus about 37 million doses, respectively — by early April, and will promote the idea of cross-vaccination. With the supply in mind, the government is overall pushing the public to use Moderna.