Covishield raised more antibodies than Covaxin, claims a preprint of the first Indian study with doctors and nurses who both received doses of one of the two Covid-19 vaccines. The study by Dr. AK Singh and colleagues states that both vaccines produced a good immune response.
Unpublished data had previously shown that Covishield was 70 percent effective after the first dose. At the same time, preliminary data from the phase 3 study confirm the effectiveness rate of Covaxin at 81 percent.
“Of 515 healthcare workers (305 male, 210 female), 95 percent showed seropositivity (higher antibodies) after two doses of both vaccines. Of the 425 Covishield and 90 Covaxin recipients, 98.1 percent and 80 percent showed seropositivity, respectively, ” says the study.
Antibody titers for Covishield higher than for Covaxin
The study shows that while both Covishield and Covaxin elicited a good immune response after two doses, the seropositivity rates and median anti-spike antibody titers were significantly higher in the Covishield arm compared to the Covaxin arm.
File photo of a health worker preparing a dose of Covishield in UP’s Ghaziabad (Image credit: PTI)
The antibody titer was 115 AU / ml (arbitrary units per milliliter) for Covishield and 51 AU / ml for Covaxin. A type of blood test, an antibody titer, determines the presence and level (titer) of antibodies in the blood.
It adds, “However, both the seropositivity rate and the mean increase in anti-spike antibodies were significantly higher in Covishield versus Covaxin Receiver.”
The anti-spike antibody level is not the same as the neutralizing antibody titer (NAb). The two are not known to correlate reliably. In fact, neutralizing antibody titers constitute only a fraction of the total anti-spike antibodies produced.
Gastroenterologist and former head of the IMA’s Kochi unit, Dr. Rajeev Jayadevan adds, “The percentage or level of anti-spike antibodies measured in the study cannot be viewed as a percentage of the protection given to the recipient.”
Breakthrough infections
Respondents who received both doses of either vaccine had a total of 27 breakthrough infections (4.9 percent). Of these, 25 were mild and two were moderate cases of breakthrough infections. There were no reported deaths from breakthrough infections.
The study represents the Risk of breakthrough infections at Covishield at 5.5 percent versus 2.2 percent at Covaxin.
File photo of health workers preparing a dose of Covaxin in Mumbai (Photo credit: PTI)
While no difference was observed with regard to gender, body mass index, blood group and any concomitant diseases, people aged 60 and over or people with type 2 diabetes had a significantly lower seropositivity rate, which indicates a comparatively lower antibody response.
Study emphasizes that vaccinations need to be increased
Both vaccines provided excellent protection in the field, according to reports from doctors across the country. According to the authors, the exact percentage is only determined in a direct comparison.
The study also shows a good safety profile for both vaccines. By and large, the study shows that the vaccines are working. It also underlined the need to speed up vaccinations in order to avert a potential third wave of infections by extending vaccination coverage.
Currently, less than four percent of the Indian population have received both doses of either vaccine, while less than 15 percent have received at least one dose.
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