A villager over 60 years old receives a booster shot in Xiahe Village, Shenyang, Dec. 27, 2022. (PHOTO:VCG)

Edited by BI Weizi

Recently, the State Council's Joint Prevention and Control Mechanism issued a plan to deploy the second dose of COVID-19 booster vaccination, which explains who should get the vaccine, and what vaccine should be given for the second booster.

Q1: Who should get a second dose of vaccine booster shot?

A: At this stage, the elderly and other vulnerable groups are at continuous risk of being infected, and vaccination is still an important tool in preventing and controlling the pandemic.

In order to proactively protect the health of communities and populations, high-risk groups, elderly people over 60, people with serious underlying diseases and people with low immunity, can receive the second booster dose six months after the first one.

Q2: What is the point of a second booster shot now?

A: Protective immunity provided by vaccines is predicated on the production of antibodies, cellular immunity and existence of immunological memory.

After vaccination, the antibody level will decrease over time. In addition, as the virus mutates, immune escape increases and antibody responses weaken.

However, cellular immunity plays a more lasting role in preventing severe illness and mortality. Studies have shown that booster shots evoke the body's immune memory cells and also boosts antibody levels, further cementing the preventive effect against serious illness and death.

As long as they are eligible for vaccination, those who have not completed booster shots should do so as soon as possible.

Q3: Which vaccines can be given for the second booster shot?

A: All thirteen vaccines that are currently approved for conditional marketing or emergency use can be used for the second booster shot. Priority is given to sequential immunizations, or vaccines containing Omicron strains, or with good cross-immunity to Omicron strains.

Sequential immunization is a vaccination strategy that uses vaccines with different technical routes for heterogenic enhanced immunity. If you have received three doses of inactivated vaccine, you can choose any of recombinant protein vaccines, adenovirus vector vaccines or vaccines using influenza virus as vectors for the second booster shot.

Q4: How safe is the second booster shot?

A: China CDC's monitoring of adverse reactions to over 3.4 billion doses, and over 1.3 billion people who have been vaccinated in China found that the incidence of adverse reactions is comparable to some other vaccines given year-round, and the incidence in the elderly is slightly lower than that of young people. People with chronic diseases such as diabetes and hypertension, which are in a stable phase, can still be vaccinated.

Q5: Is a second booster shot recommended to people after testing positive for COVID-19?

A: According to the current technical guidelines for vaccination against the novel coronavirus, there should be an interval of at least six months between infection and vaccination.

At present, hybrid immunity, which is the immunity acquired from both prior infection and vaccination, offers better protection against COVID -19 than single infection-induced immunity. So a second booster shot is still recommended wherever possible.