People in Beijing are getting familiar with coffee-cup-shaped COVID-19 vaccine devices.

Inhale, hold for five seconds, then breathe normally. That's it. Within seconds, the inhaled aerosolized COVID-19 vaccine reaches the upper respiratory tract and lungs, where immunity is triggered.

Having watched the whole process, quite a few senior people joined in.

China is rolling out inhalable COVID-19 boosters and many appointments are booked by the elderly.

Yan Changrong, 81, experienced the process at Huayuanlu Community Health Service Center in Beijing.

"When the weather is cold, it is difficult for us old people to take off our clothes," Yan said. "[The inhaler] saves a lot of trouble and doesn't hurt as much as an injection. It even tastes a little sweet."

Experts say inhaled vaccines trigger immunity at our body's first line of defense, the mucous membranes, in addition to humoral and cellular immunity that traditional injectable vaccines trigger.

"It's normal to have a dry mouth after inhaling the vaccine. Drinking water will relieve it," said Zhou Xin, head of the Preventive Health Section at the center. "In addition, PCR tests can still be done normally after this. The results will not be affected."

More than 90 percent of people in China have been vaccinated against COVID-19. But the proportion of vaccinated senior people is still concerning. As of November 28, a little over 86 percent of China's senior citizens over the age of 60 had been fully vaccinated against COVID-19, but only 65 percent of those over the age of 80 were fully vaccinated.

"Three years into the epidemic, almost all willing and eligible people have been vaccinated, except for some elderly people who have their own concerns," Jia Zhiping, section chief of Huayuanlu Community Office, told CGTN.

Those who have their concerns include the elderly with underlying medical conditions, who fear that vaccination could worsen their illness. Sixty-year-old Ms Wang is among them.

"I have hypertension and was cautious about getting my first dose of COVID vaccine," said Wang. "Later, I was told by experts that people with basic diseases can be vaccinated when their health condition is stable, so I took two shots successively."

"Then, I heard the booster is inhalable, and the effect is better, so, I came to try it," she added.

After inhaling the vaccine, Wang told CGTN she felt fine and agreed that people should take care of their own health and protect themselves before others by boosting their immunity.