Comparison of NT50 levels of five COVID-19 strains at different time points The figures in this article are all research paper figures
According to Worldmeter real-time statistics, as of February 16, 2022, there have been more than 410 million confirmed cases of COVID-19 and more than 5.85 million deaths worldwide. At present, a variety of vaccines have been used to help significantly reduce the severe illness and mortality rates caused by the new crown virus, but public health is still at risk due to the rapid development of the epidemic and the weakening of vaccine protection after vaccination.
On February 15, a study on the protective efficacy of mRNA after COVID-19 vaccination showed that the protective effect of the vaccine weakened over time, and after six months of two doses, the vaccine was basically ineffective against the Delta and Omicron strains.
Serum samples of 48 healthcare workers who received the Modena vaccine (Moderna mRNA-1273) or the Pfizer vaccine (BioNTech BNT162b2) were collected at four time points, including before the first vaccination, three weeks after the first vaccination, one month after the second vaccination, and six months after the second vaccination, and the neutralization antibody (nAb) response was continuously monitored.
The research team used the pseudotyped virus system to neutralize five strains of the new coronavirus (D614G, Alpha, Beta, Delta, Omicron) and neutralized antibody titers, a key predictor of preventing viral infection, as an indicator of vaccine effectiveness, and measured neutralization activity with semi-maximum neutralizing potency (NT50) data indicators.
The data results showed that after the first dose of mRNA vaccine, the D614G, Alpha, Beta, and Delta strains all induced a strong neutralizing antibody response compared with before vaccination, while 93.8% of the samples of the Omiljung strain were below the lower detection limit of the neutralizing antibody titer. After the second dose, the average neutralizing antibody titer for the D614G, alpha, beta, delta strains increased by 2 to 3 times, and 25.0% of the samples for Omiqueron were still below the lower limit of the detection of neutralizing antibody titers.
Correlation between time and NT50 levels
What's more, the researchers observed that 1 month to 6 months after completing the two doses of vaccination, the titers of neutralizing antibodies against alpha, beta, and delta strains all declined. Among them, 56.3% and 89.6% of the samples had neutralizing antibody titers below the detection limit for Delta and Omi kerong, respectively.
The team also explored the mathematical relationship between time and neutralizing antibody titers and found that every 22 weeks, the semi-maximum neutralizing potency of the D614G, Alpha and Delta strains was reduced by about 90%. Every 37 weeks, the semi-maximum neutralizing potency of beta strains drops by about 90 percent.
The paper concluded that the neutralizing antibody response from the two-dose vaccine regimen weakened over time and was largely ineffective against Delta and Omiljun strains after 6 months. The results of the above study show the need for vaccination to boost the needle. Future studies will need to further track the persistence of the neutralizing antibody response after vaccination to enhance injections. As variant strains of covid-19 continue to emerge and people continue to seek ways to contain the outbreak, understanding the interaction between vaccine durability and viral evolution is critical.
The surging news reporter noted that on February 15, the World Health Organization released a weekly epidemiological report on new crown pneumonia, pointing out that the current Olmiqueron strain has replaced the Delta strain as the main epidemic strain in the world, and 98.3% of the recently reported gene sequences of the new crown virus in the world are Omiljung strains. Based on Denmark's epidemic data, the Omil kerong subtype variant strain BA.2 was 30% more contagious than the original Omi kerong strain BA.1.
According to foreign media BBC, Nature reported that in late January 2022, Pfizer and Modena successively announced that the new version of the vaccine against the Omiljung strain has started clinical trials.