The Delta (Delta/δ) variant, which is characterized by high transmission capacity, rapid spread, and atypical onset of symptoms, has been shown to significantly reduce the neutralization level of vaccine antibodies, which in turn may affect the effectiveness of the vaccine. Thankfully, according to available data, people who have been fully vaccinated with the new crown vaccine have a significantly lower risk of hospitalization and severe illness than those who have not been vaccinated, regardless of the setting in which the variant is prevalent. In addition, in the analysis of confirmed cases of Delta variant infection in China, the data showed that patients who received the New Crown vaccine had a shorter time from diagnosis to positive antibody conversion, higher Ct values (the higher the Ct value, the lower the viral nucleic acid concentration), and shorter reported hospitalization times than those who were not vaccinated. In other words, although there may still be some risk of infection after vaccination, the vaccine is clearly protective. In addition, there is a relationship between the level of neutralizing antibodies produced by the body after vaccination and effectiveness. For the commonly used new crown inactivated vaccine, the peak neutralizing antibody after vaccination is usually 28 days after the second dose. Therefore breakthrough infection should also be considered in two aspects: first, the short time to complete vaccination before infection, the body may not have produced enough neutralizing antibodies against the new crown virus, and the lack of protection leads to the risk of being infected; on the other hand, the level of antibodies in the body will continue to decline over time, and the risk of infection may increase accordingly. Fortunately, after vaccination, the body will develop an “immune memory” and the immune system will rapidly produce a large number of neutralizing antibodies when next exposed to the virus or vaccine antigen, so even if the body does not have neutralizing antibodies against the virus, it does not mean that the protective effect of the vaccine will disappear. Of course, the maximum duration of protection by the new vaccine is not yet determined, and the need for future booster doses should be determined in the light of the epidemic situation and subject to the information released by the state. In particular, it is important to be aware of the need for daily protection even after a full course of vaccination. It is also necessary to keep your home ventilated and disinfected, wear a good mask when you go out, wash your hands regularly, exercise regularly, and maintain good habits. Only with multiple protective measures can we minimize the infection of NCCV and maximize the protection of normal life. Reviewed by Chen Liyan, Deputy Chief Physician, Department of Infectious Diseases, The Second Hospital of Harbin Medical University, Shao Yinan, Co-Author, “Talking about Vaccines”, Director, Beijing Biological Products Research Association