Francisco Hernandez-Bernal
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Maria del Carmen Ricardo-Cobas
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Yenima Martin-Bauta
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Zadis Navarro-Rodriguez
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Marjoris Pinera-Martinez
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Aim: To evaluate the safety and immunogenicity of a SARS-CoV-2 recombinant spike protein vaccine (Abdala), administered intramuscularly in different strengths and vaccination schedules.
Method: A phase 1-2, randomized, double-blind, placebo-controlled trial was done. Subjects were randomly distributed in 3 groups: placebo, 25 and 50 μg RBD. The product was applied intramuscularly, 0.5 mL in the deltoid region. During the first phase, two immunization schedules were studied: short (0-14-28 days) and long (0-28-56 days). In phase 2, only the short scheme was evaluated. The main endpoints were: safety and proportion of subjects with seroconversion of anti-RBD IgG antibodies to SARS-CoV-2. Blood samples were collected in several points according to the corresponding vaccination schedule to determine the level of RBD-specific IgG antibodies (seroconversion rates and geometric mean of the titers), the percentage of inhibition of RBD-ACE-2 binding and levels of neutralizing antibodies.
Results: The product was well tolerated. Severe adverse events were not reported. Adverse reactions were minimal, mostly mild and local (from the injection site), resolved in the first 24-48 hours without medication. In phase 1, at day 56 (28 days after the third dose of the short vaccination schedule, 0-14-28 days) seroconversion of anti-RBD IgG was seen in 95.2 % of the participants (20/21) for the 50 μg group and 81 % of the participants (17/21) for the 25 μg group, and none in the placebo group (0/22); whereas neutralizing antibodies to SARS-CoV-2 were seen in 80 % of the participants (8/10) for the 50 μg group and 94.7% of the participants (18/19) for the 25 μg group. For the long schedule, at day 70 (14 days after the third dose) seroconversion of anti-RBD IgG was seen in 100% of the participants (21/21) for the 50 μg group and 94.7% of the participants (18/19) for the 25 μg group, and none in the placebo group (0/22); whereas neutralizing antibodies to SARS-CoV-2 were seen in 95 % of the participants (19/20) for the 50 μg group and 93.8% of the participants (15/16) for the 25 μg group In phase 2, at day 56 seroconversion of anti-RBD IgG was seen in 89.2% of the participants (214/240) for the 50 μg group, 77.7% of the participants (185/238) for the 25 μg group, and 4.6% in the placebo group (11/239); whereas neutralizing antibodies to SARS-CoV-2 were seen in 97.3% of the participants (146/150) for the 50 μg group and 95.1% of the participants (58/61) for the 25 μg group.
Conclusion: Abdala vaccine against SARS-CoV-2 was safe, well tolerated and induced humoral immune responses against SARS-CoV-2 among adults from 19 to 80 years of age.
Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy adults aged 60 years and older: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial