On Wednesday, senior U.S. health officials announced in a joint statementNew data show that the protective effect of the vaccine weakens over time, and the United States will begin to distribute COVID-19 vaccine enhancements on a large scale next month.

A statement signed by Rochelle Walensky, director of the US Centers for Disease Control and Prevention (CDC), Janet Woodcock, acting director of the US Food and Drug Administration (FDA), and Anthony Fauci, chief medical adviser of the White House, said:

The available data clearly show that after initial vaccination, the protective effect against SARS-CoV-2 infection decreases over time, and the superimposed Delta variant virus spreads rapidly, and we are beginning to see evidence that the protective effect of the vaccine against mild and moderate diseases is reduced. According to our latest assessment, current vaccine protection against serious illness, hospitalization and death is likely to diminish in the coming months, especially for those at higher risk or who have been vaccinated in the early stages of vaccination promotion.

So, officials sayU. S. agencies are preparing to start providing booster injections to all Americans from the week of September 20, eight months after the second dose of Pfizer Inc or Moderna Inc vaccine.Officials also said that people who received a single dose of Johnson & Johnson vaccination may also need to strengthen their vaccination, but are still waiting for more data in the coming weeks before making formal recommendations.

The United States has vigorously promoted the vaccination process mainly because the Delta mutation has led to a resurgence of the COVID-19 epidemic in recent months, while the surge in cases is more obvious in areas where vaccination lags behind. As of the 15th, Florida, Louisiana, Hawaii, Oregon and Mississippi all broke the record for a seven-day average daily increase. In addition, the study found that the effectiveness of Pfizer Inc vaccine against Delta virus was only 42% in July this year. Overall data show that vaccines provide strong immunity at an early stage, but their effectiveness decreases sharply over time.

Recently, Noubar Afeyan, co-founder of Moderna Inc, predicted that one day enhanced vaccination will become the norm, and that it may need to be strengthened every year, just like some kind of flu. Afeyan also said they were testing a half-dose strengthening needle that "seems to be very effective."

Driven by the news, vaccine stocks MRNA narrowed down to less than 1.0 per cent to above $401, while US stocks fell to $386.21 at the start of the session. Pfizer Inc Pharmaceuticals (PFE) expanded to 2.3 per cent, setting an all-time intraday high of $51.59. Market analysts believe that, as industry leaders, Pfizer Inc and Moderna Inc's vaccine enhancements may have greater pricing power before more competitors pour into the market.