According to CNBC, a news broadcaster specializing in economics on the 8th (local time), Pfizer and BioNTech said, “Even if you inoculate the vaccine twice so far, it is the” highest level “for all variants. It may build immunity, but stay alert and continue to update the booster shot vaccine. ” With the approval of the US health authorities, the two companies are expected to begin clinical trials of booster shots on Delta strains as early as August. The reason why these two companies have started to develop booster shots separately is that the Delta strain is spreading rapidly all over the world, but the preventive effect of vaccination so far has passed 6 months. This is because it is supposed to decrease. Pfizer is looking for ways to increase production, as demand for vaccines is expected to increase once booster shots are given.