A phase 1b-2 clinical trial has shown that two doses of the COVID19 vaccine made by AstraZeneca and Oxford University might not be effective against the B1351 variant of coronavirus, which has been found in South Africa. The findings of this early trial have been released in the New England Journal of Medicine. This trial is known as a double-blind multicenter study. It has been done by experts from the South African Medical Research Council Vaccines and Infectious Disease Analytics Research Unit. During the study, experts have tested the safety and efficacy of the AstraZeneca ChAdOx1 nCov-19 vaccine. Two doses of the vaccine have been given to HIV-negative people who have been in the age group of 18 to 64 years. Participants have been given either two regular doses of the vaccine or a placebo in a 1:1 ratio in the gap of 21 to 35 days from June 24 to November 9, 2020. Median follow-up after the second dose has been 121 days, said the experts. Around 750 participants have been included in the study. Nearly 19 participants have been found to have mild to moderate symptoms of COVID19 for more than 14 days after the second dose of the vaccine as compared to 23 people out of those who have been given a placebo. The cases of COVID19 in the vaccine group have been 731 per 1000 person-years as compared to 93.6 per 1000 person-years in the placebo group for an efficiency of 21.9 percent. Around 39 COVID19 cases out of 42 total cases have been caused by the B1351 variant, said the experts. The efficacy of the vaccine against this variant has been 10.4 percent. All patients with COVID19 have been dealing with mild infections and none of them have been admitted to the hospital.
The authors of the study have said that they have seen in the trial that two doses of the AstraZeneca vaccine have not been effective enough against the B1351 variant. The vaccine has not been able to prevent mild to moderate COVID19 infection. They have said that the lack of efficiency of the vaccine against the B1351 variant needs to be measured in the context of the 75 percent efficacy in averting mild to moderate infection with onset at least 14 days after even the single dose of the vaccine that was seen before this strain has been found in South Africa. The rates of adverse events have been the same in the placebo group and vaccine group. Only one adverse event in the vaccine group has occurred after the first dose, which has been a fever of 40 0C. However, the fever has subsided after 24 hours. There have been no adverse events after the second dose of the vaccine. The authors of the study have said that they have not seen severe cases of COVID19 during the study, which might be a sign of the relatively young mean age of the participants. Therefore, the study has not been able to identify whether the AstraZeneca vaccine will be effective against the severe infection caused by the B1351 variant. They have said that the degree to which the efficiency of other COVID19 vaccines can be affected by the strains with mutations equal to those of the B1351 and P1 variant, which has been found in Brazil might rely on the level of antibodies produced by vaccination. Experts have said that they are unsure that an improved antibody retort due to a larger gap between the first and second doses of the vaccine might give a better antibody response against the B1351 strain than what has been seen in the trial.
The authors of the study have said that though the development of the second-generation shots has started that might be effective against the strains such as B1351 and P1, but the vaccines which have been formulated against the original strain are going to be available for the rest of 2021. They have said that until new vaccines are available, health experts will have to rely on the AstraZeneca vaccine. The South African officials have stopped the rollout of this vaccine to examine whether it is effective against the new strains. The country has started using the one-shot vaccine developed by Johnson & Johnson. Many health care workers have been vaccinated with Johnson & Johnson vaccine in South Africa. Health experts are worried that many new strains of the virus might be spreading around carrying the same kind of mutations.