Posted for those who like to know the concerns and the truth about the Chinese vaccines. Others can ignore and stay high. I have no problem with it.
The CoronaVac vaccine has been developed by Sinovac Biotech in China and is based on the inactivated whole-virus. This vaccine has been approved for emergency use in Thailand and has also been used in vaccination programs in many low-income countries.
Infections in Thailand contain the B.1.1.7 (Alpha), B.1.351 (Beta), and B.1.617.2 (Delta) variants. A new study evaluates the efficacy of vaccine- and infection-induced antibodies against these variants.
The team assessed NAb potency against the prototypic strain containing the original spike sequence (WT) compared to that against the 3 VOCs using sera derived from a cohort of healthcare workers who received a full 2-dose regimen of CoronaVac. Sera from two other cohorts consisting of COVID-19 patients who had been hospitalized in 2020 and 2021 were evaluated for comparison. We found that, despite equally robust production of S1-RBD-binding IgG and 100% seropositivity,
This is their conclusion.
"Although NAb titers are not an exclusive immune correlate of protection, they are highly predictive of immune protection from symptomatic SARS-CoV-2 infection. Based on our data, although there was robust production of S1-RBD-binding IgG and 100% seropositivity, NAb-mediated protection was markedly reduced (and in many cases undetectable) against the 3 VOCs compared to WT in sera from all groups. NAb potency against Alpha and Beta were comparable in our CoronaVac vaccinee sera; this is inconsistent with a previous report that Beta shows more resistance to neutralization than Alpha in CoronaVac vaccinee sera collected 14 days after the second dose when tested using a pseudovirus neutralization assay. Worryingly, the Delta strain, which is the most transmissible, possibly among the most virulent of all VOCs identified to date , and is rapidly becoming a dominant strain in many countries, appears to be most refractory to neutralization. Lastly, our study highlights a low degree of neutralization-afforded protection mounted by CoronaVac when compared to natural infection. Further booster doses, heterologous or otherwise, beyond the conventional 2-dose regimen may be needed to maintain long-term anamnestic response. We also underscore a potential risk for reinfection in previously infected individuals, particularly with VOCs. Amid steady NAb decay over time and the continued emergence of divergent SARS-CoV-2 strains, it is imperative to maintain effective mitigation strategies and to continue monitoring vaccine efficiency in areas with circulating VOCs."
PS: The take home message is highlighted in the above paragraph. In layman terms NAb titers elicited by CoronaVac are much lower when compared to natural infection. Also they will need a booster from another vaccine for long term protection.
PPS: This is similar to what Pani Jay and the Sri J team carried out recently and made a big celebration. But the facts are far from it. Below is what I wrote on that thread as a reply.
The Thai team enforces what I said. Note this study in on SinoVac but it cannot be much different to Sinopharm as they both are similar.
On a cursory glance at the paper what they say is -
"95% of the vaccinees seroconverted, although the seroconversion rates were significantly lower (p<0.001) in individuals >60 years (93.3%) compared to those who were 20 to 39 years (98.9%)......"
Note that this is does not refer to the vaccine’s efficacy at all, it simply is the vaccine’s seroconversion rate. The seroconversion rate detects whether the vaccine produces COVID-19 antibodies.
This is almost reinventing the wheel probably because the Chinese since last December 2020 or before said their vaccines have a seroconversion rate of 97%. But they never published the efficacy. Only roundabout figures were used from the Gulf areas.
The seroconversion rate is not a proof that the vaccine protects against COVID-19 or the vaccine efficacy is 93%.
The CoronaVac vaccine has been developed by Sinovac Biotech in China and is based on the inactivated whole-virus. This vaccine has been approved for emergency use in Thailand and has also been used in vaccination programs in many low-income countries.
Infections in Thailand contain the B.1.1.7 (Alpha), B.1.351 (Beta), and B.1.617.2 (Delta) variants. A new study evaluates the efficacy of vaccine- and infection-induced antibodies against these variants.
The team assessed NAb potency against the prototypic strain containing the original spike sequence (WT) compared to that against the 3 VOCs using sera derived from a cohort of healthcare workers who received a full 2-dose regimen of CoronaVac. Sera from two other cohorts consisting of COVID-19 patients who had been hospitalized in 2020 and 2021 were evaluated for comparison. We found that, despite equally robust production of S1-RBD-binding IgG and 100% seropositivity,
This is their conclusion.
"Although NAb titers are not an exclusive immune correlate of protection, they are highly predictive of immune protection from symptomatic SARS-CoV-2 infection. Based on our data, although there was robust production of S1-RBD-binding IgG and 100% seropositivity, NAb-mediated protection was markedly reduced (and in many cases undetectable) against the 3 VOCs compared to WT in sera from all groups. NAb potency against Alpha and Beta were comparable in our CoronaVac vaccinee sera; this is inconsistent with a previous report that Beta shows more resistance to neutralization than Alpha in CoronaVac vaccinee sera collected 14 days after the second dose when tested using a pseudovirus neutralization assay. Worryingly, the Delta strain, which is the most transmissible, possibly among the most virulent of all VOCs identified to date , and is rapidly becoming a dominant strain in many countries, appears to be most refractory to neutralization. Lastly, our study highlights a low degree of neutralization-afforded protection mounted by CoronaVac when compared to natural infection. Further booster doses, heterologous or otherwise, beyond the conventional 2-dose regimen may be needed to maintain long-term anamnestic response. We also underscore a potential risk for reinfection in previously infected individuals, particularly with VOCs. Amid steady NAb decay over time and the continued emergence of divergent SARS-CoV-2 strains, it is imperative to maintain effective mitigation strategies and to continue monitoring vaccine efficiency in areas with circulating VOCs."
PS: The take home message is highlighted in the above paragraph. In layman terms NAb titers elicited by CoronaVac are much lower when compared to natural infection. Also they will need a booster from another vaccine for long term protection.
PPS: This is similar to what Pani Jay and the Sri J team carried out recently and made a big celebration. But the facts are far from it. Below is what I wrote on that thread as a reply.
The Thai team enforces what I said. Note this study in on SinoVac but it cannot be much different to Sinopharm as they both are similar.
On a cursory glance at the paper what they say is -
"95% of the vaccinees seroconverted, although the seroconversion rates were significantly lower (p<0.001) in individuals >60 years (93.3%) compared to those who were 20 to 39 years (98.9%)......"
Note that this is does not refer to the vaccine’s efficacy at all, it simply is the vaccine’s seroconversion rate. The seroconversion rate detects whether the vaccine produces COVID-19 antibodies.
This is almost reinventing the wheel probably because the Chinese since last December 2020 or before said their vaccines have a seroconversion rate of 97%. But they never published the efficacy. Only roundabout figures were used from the Gulf areas.
The seroconversion rate is not a proof that the vaccine protects against COVID-19 or the vaccine efficacy is 93%.
..
