Fully vaccinated people in China can now choose to receive a different shot from their original inoculation as a booster in a process called sequential immunization.

Here are some important details you should know about the sequential booster immunization.

A medical worker administers a dose of the recombinant COVID-19 vaccine (adenovirus type 5 vector) to a resident at a temporary vaccination site in Haidian district of Beijing, May 20, 2021. [Photo/Xinhua]

1. What is sequential immunization?

Sequential immunization is a vaccination strategy that uses different types of vaccines for original and booster inoculations.

2. Who can get a sequential COVID-19 booster shot?

People must meet the following requirements to be eligible:

- Over 18 years old;

- Fully vaccinated with inactivated vaccines produced by Sinovac, Sinopharm Beijing or Sinopharm Wuhan;

- At least 6 months have passed since a second dose has been inoculated.

3. What are the vaccine options for a sequential booster shot?

Those eligible can choose between a protein subunit COVID-19 vaccine made by Anhui Zhifei Lingcom Biopharmaceuticals and a viral vector vaccine developed by CanSino Biologics.

4. What are the advantages of sequential immunization?

Sequential immunization is often rolled out when dealing with tricky and fast-mutating viruses.

This method is favored for combining the advantages of different vaccines and preventing people at risk of side effects for one particular kind of vaccine from going through them again.

Compared with a homologous booster vaccination strategy, sequential immunization can improve the breadth, strength, durability and functionality of immune response.

People receive COVID-19 vaccines at a temporary vaccination site in Nan'an district of Chongqing, Southwest China, March 27, 2021. [Photo/Xinhua]

5. Has the sequential immunization strategy been adopted in other countries?

A number of countries in the Americas, Europe and Southeast Asia have already begun using different vaccines from those originally given for their booster shot programs.

The World Health Organization said it supports a flexible approach to boosting with a same or different dose.

6. What is the safety and efficacy of the sequential immunization strategy?

The approach has proved to be safe and effective based on domestic and foreign studies.

No additional side effects were found to be linked to a sequential booster.

7. Do I need to have both homologous and sequential booster vaccinations?

Research has shown either boosting with a dose that is the same as the initial inoculation or with a dose developed with a different technology is effective at further improving immunity against COVID-19. The eligible group only needs to choose one of them.