The Lancet: The University of Hong Kong compares Sinovac head-to-head with mRNA vaccines to prevent Omicron

With the large-scale epidemic of the new crown virus, new virus mutant strains continue to appear, Alpha, Beta, Gamma, Delta, Omicron, etc.
, some of which have stronger infection ability or stronger immune escape ability, and the world's most concerned is the Omicron mutant strain
.

Several studies have shown that vaccination can produce antibodies in the body, which can provide effective protection against adverse health consequences such as hospitalization and death, although the third dose of vaccination can effectively enhance antibodies, but the immune protection against Omicron BA.
2, BA.
4/5 remains to be studied
.

Recently, researchers from the Li Ka Shing School of Medicine at the University of Hong Kong, China, published an article titled "Three-dose vaccination-induced immune responses protect against SARS-CoV-2 Omicron BA.
2:A in The Lancet Regional Health-Western Pacific" population-based study in Hong Kong"
.

The study showed that timely vaccination of the third booster dose can significantly reduce the incidence of Omicron BA.
2 breakthrough infection and the severity of the disease, with 2 doses of Sinovac inactivated vaccine, the BA.
2 breakthrough infection rate was 44.
1%, and with 3 doses of Sinovac, the breakthrough infection rate dropped to 19.
4%.

With 2 doses of BNT162b2, the breakthrough infection rate of BA.
2 was 46.
2%, and with 3 doses of BNT162b2, the breakthrough infection rate dropped to 13.
1%.

In addition, the third dose of vaccination activated spike protein-specific memory B cells and Omicron cross-reactive T cell responses, helping to reduce the severity of breakthrough infections and diseases, regardless
of vaccine type.

Importantly, 3 doses of Sinovac or BNT162b2, BA.
2 breakthrough infection enhanced cross-reactive memory B cells and also reduced infection with other variants of Omicron (BA.
2.
12.
1, BA.
4/5).

In the study, the researchers analyzed 470 civil service participants who received two and three doses of the vaccine between January and March 2022, during which the Omicron BA.
2 strain
was predominantly circulating in Hong Kong.

Among them, 169 participants received 2 doses of BNT162b2, 168 participants received 3 doses of BNT162b2, 34 received 2 doses of Sinovac vaccine, 67 received 3 doses of Sinovac vaccine, and 32 people received 2 doses of Sinovac 1 dose of BNT162b2
.

During the study period, a total of 130 people (27.
7%) were confirmed as Omicron BA.
2 breakthrough infection with no sex differences
.
The incidence of breakthrough infection with 2 shots of BNT162b2 was 46.
2%, and the incidence of breakthrough infection with 2 shots of Sinovac was 44.
1
%.

For the third dose, the infection rate of homologous BNT162b2 was 13.
1%, and the infection rate of homologous Kexing was 19.
4%, which was a significant decrease
compared with the two doses.

In addition, the 2-dose Sinovac 1-dose BNT162b2 vaccination group had the lowest incidence of infection at 6.
3%
compared to homologous.

Importantly, an analysis of people who received 3 doses of the vaccine found that the third dose of vaccination activated spike protein-specific memory B cells and Omicron cross-reactive T cell responses, helping to reduce the severity of breakthrough infections and disease, regardless
of vaccine type.

Activation of spike-specific memory B cells with a third dose of vaccine

In addition, whether it is 3 doses of Sinovac or BNT162b2, BA.
2 breakthrough infection enhances cross-reactive memory B cells in 3-dose vaccine recipients, which may reduce infection with other variants of Omicron (BA.
2.
12.
1, BA.
4/5).

In conclusion, studies have shown that a 3rd dose of vaccine should be given promptly, which provides better protection and lower
disease severity than 2 doses.
In people who received 3 shots of the vaccine, BA.
2 breakthrough infection enhanced cross-reactive memory B cells, which may reduce infection
with other variants of Omicron.