Effectiveness of combined injections of Covid-19 vaccines

However, scientists have shown that mixing vaccines is more effective than injecting the same vaccine.

The effectiveness of combined vaccination

A study by German scientists published in the journal Nature Medicine showed that the study group injected with a combination of the ChAdOx1 nCoV-19 vector vaccine (AstraZeneca) and an RNA vaccine (BNT162b2, Pfizer or mRNA-1273, Moderna) or a combination of two RNA vaccines produced better humoral and cellular immunity than the control group injected with two identical doses of vaccine.

The study also showed that the group of subjects injected with the combined vaccine produced 9 times more specific antibodies than the group injected with the same vaccine. The number of CD4 T lymphocytes and CD8 T lymphocytes specific to the group injected with the combined vaccine produced 4 and 3.5 times more than the group injected with the same vaccine.

Illustration photo. Source internet.

Mixing vaccines has been proposed by scientists since the 1990s, and some have proven effective. Rodolphe Thiébaut, professor of epidemiology at the University of Bordeaux in France, said mixing vaccines essentially “presents” the immune system in different ways with different antigens to create protective immune responses.

Mixing vaccines works particularly well with vaccines that use modified viruses, such as those from AstraZeneca, Sputnik V, Johnson & Johnson, and CanSino Biologics. With these vaccines, the body can generate immunity against the carrier virus (such as adenovirus) and immunity against the Sars Cov-2 virus antigen. Some scientists believe that in some subjects vaccinated with these vaccines, immunity against the carrier virus may be too strong, making immunity against the Sars Cov-2 virus weaker.

Therefore, combining two vaccines can enhance immunity compared to injecting one vaccine.

Safety of combination vaccines

The UK clinical trials on mixed vaccines are in phase 3. The phase 2 results show the safety of mixing vaccines during the study phase. However, the safety of each vaccine is assessed over a very long period of time, so these studies will continue to monitor the subjects and assess the safety of each vaccine as well as the safety of the combination of vaccines.

From a public health perspective, Prof Thiébaut said mixing vaccines could help overcome this pandemic by accelerating the rollout of vaccinations. “It is good news for the government’s flexibility to use what they have, backed by scientific evidence, to combat the rapidly evolving variants of the Sars Cov-2 virus,” he said.

Faculty of Medicine, Dai Nam University (synthesis)