CHINA National Pharmaceutical Group (Sinopharm) will need to assess results from overseas Phase III clinical trials to decide whether its two-shot COVID-19 vaccine should be followed by a booster shot, a company executive said on Sunday. Regulators and vaccine developers are looking at whether booster doses are necessary amid concerns that emerging variants of the new coronavirus might weaken protection of vaccines designed against older strains. "The preliminary results so far showed that the booster vaccination can effectively increase the neutralizing antibody titer and antibody persistence, and also effectively improve the vaccine's ability to resist mutations," Zhang Yuntao, vice president…