A girl gets a shot of the Sinovac COVID-19 vaccine at a school in Bogota, Colombia, on Monday. (FERNANDO VERGARA / AP)

China-made vaccines are helping Latin American countries roll out COVID-19 booster campaigns as governments step up their pandemic response amid concerns over new virus variants.

Nearly 26 percent of Chile's population have received CoronaVac booster shots in recent months, after kicking off its COVID-19 inoculation drive in December.

Colombia is also rolling out a vaccine booster campaign, but has not yet extended it to the entire population.

"Booster vaccination is very important. At this moment, the COVID-19 vaccine booster shot is being applied to people over 70 years of age and to people with any immunosuppression condition," said Luis Jorge Hernandez, a member of the Covida project at the University of The Andes in Colombia.

Hernandez said it is essential to administer this third dose, especially to people over the age of 70, as they have seen a decrease in the immune response in people over this age.

He added that he hopes the booster campaigns will be extended soon to cover people with medical issues such as cancer and lupus, as well as to healthcare workers and the general population.

An analysis of data from Chile released in October found that a third shot can significantly increase vaccine effectiveness, raising it from 56 to 80 percent, and boosting effectiveness against hospitalization to 88 percent. Some 3.6 million people in Chile have received a booster shot to date.

"When receiving a booster dose with any vaccine, the risk (of hospitalization) decreases," said Sebastian Ugarte, director of the Critical Care Medicine Program at Andres Bello University in Chile. If the third dose was Sinovac, the effectiveness increased to 88 percent.

As such, many governments around the world are now implementing booster programs.

In Chile, booster shots have helped give the country reassurance to open up its borders.

Chen Zhengming, an epidemiology professor at the University of Oxford, noted that many countries such as the United Kingdom, Israel, the United States and Singapore are implementing booster programs.

"Enough evidence shows that after about six to nine months of the initial two doses of vaccine, the antibody levels start to wane significantly. A third dose will greatly boost the antibody levels, fivefold or tenfold depending on the type of vaccine," Chen said.

With countries planning to relax public health measures, a third dose can "save many lives", said Benjamin Cowling, professor and head of the epidemiology and biostatistics division at the University of Hong Kong.

More than 1.5 billion vaccine doses made by China's Sinovac Biotech and Sinopharm have been distributed to more than 100 countries. Some of these countries have built their vaccination campaigns around the availability of Chinese jabs.

The writer is a freelance journalist for China Daily.