Q&A on vaccine protective effects, booster shot

Doses of the Chinese Sinopharm vaccine against the coronavirus disease (COVID-19) are seen. [Photo/Agencies]

The National Health Commission has responded to key public concerns about COVID-19 vaccines and disease control policies amid a resurgence of novel coronavirus fueled by the Delta variant in recent weeks.

1. How durable is a COVID-19 vaccine's protective effects?

Available data shows that like other vaccines, antibody levels in vaccinated people will go down as time goes by. Six months after full immunization, neutralizing antibodies in people aged 18 and above inoculated with any vaccines drop by 1.4 to 12.4 times.

But declining antibody levels is not equal to loss of vaccine-induced protection. Research is underway to figure out how much of the decline will make protective effects disappear.

Some studies show that a booster shot delivered six to 12 months after initial immunization can markedly increase neutralizing antibodies in a short span. This suggests that earlier vaccines have triggered very good immunological memory in human bodies, which can last at least a year.

2. Is it necessary to get a COVID-19 booster shot?

There isn't enough evidence now to support delivering COVID-19 booster shots to individuals in the general public who have been vaccinated within a year.

However, for the elderly with weak immune systems, those suffering from chronic illnesses, workers at higher risk of contracting the virus, or people planning to travel to high-risk areas, research is underway to determine whether a booster dose is needed six to 12 months after initial immunization, and if so, then when the booster shot should be rolled out.

3. Can we mix and match different types of COVID-19 vaccines?

During China's current mass immunization campaign, different types of vaccines cannot replace each other.

If a recipient is administered an inactivated vaccine, later inoculations must use inactivated vaccine. If the recipient is given a CHO recombinant protein subunit vaccine, then the second and third shot must also be the subunit vaccine.

If a recipient cannot finish an inoculation with shots from one company, he or she must use the same type of vaccine to complete vaccination.

4. How is vaccination for the elderly and teenagers going?

Seniors aged 60 and above have now been fully incorporated into the mass vaccination campaign. As of July 28, China had vaccinated 150 million people in this age group.

Vaccinations targeting youths aged 12 to 17 are also progressing smoothly, with 12.48 million in this age group vaccinated as of July 28.

5. Can current antivirus measures tackle virus mutations?

Yes, for two reasons.

The first is that new virus strains are still of the coronavirus type, and its source of infections and transmission mode are clear.

Second, China's disease control measures have been effective in stemming nearly 30 local outbreaks in provinces like Guangdong, Liaoning and Yunnan. Their effects are obvious.

6. Can we travel this summer?

People in medium- and high-risk areas should cancel their trips. People in other areas should check the risk status in planned destinations and postpone trips to areas at medium or high risk of the virus's spread.

Wherever one goes, he or she should abide by personal preventive measures, such as mask wearing, washing hands regularly and avoiding indoor gatherings. In outdoor areas, keeping a distance is recommended.

The elderly and people with chronic diseases, especially those who have not been fully vaccinated for at least 14 days, should avoid traveling to other regions.

7. Why keep wearing masks?

Even fully vaccinated people should keep their masks on.

There is no guarantee that vaccines can provide protection for all individuals, and it will take time for vaccinated people to generate antibodies. In addition, the virus can still spread easily before herd immunity is established in a population.

Mask wearing is recommended in public spaces with poor ventilation, including transportation vehicles and elevators, as well as at public service facilities such as cash registers at supermarkets or bank counters.

At hospitals, people must wear masks.

Source: National Health Commission