Scientific blog

Coronavirus vaccines – myths and reality

18 January, 2021

Vaccination, without a doubt, is the most effective measure possessed by humanity to mass-counter the infection. That is why we must be very careful and scrupulous of all the information focusing on the negative effects of the vaccines for the false interpretations not to delay vaccination rollout.

Regarding the "damages" caused by the coronavirus vaccine, for example, there have been reports on the number of severe allergic reaction (anaphylaxis) cases, which is actually extremely rare, however, the tables circulating on the social network indicated that allegedly over 3 thousand out of 112 thousand vaccinated people had complications. In reality, the primary source of the data indicates that it is about accounting cases with severe complications and that over 3 thousand out of 112 thousand people were observed for it. Whether it was intentional or not, the context of what was being accounted was misread.

another case, there was a discussion alleging that HIV/AIDS was detected in people who received the coronavirus vaccine. In reality, it was a candidate vaccine developed by the University of Queensland, Australia, and was terminated in the first phase of trials because vaccinated people had false-positive HIV test results. Of course, it was not about the vaccinated people acquiring HIV (as social media "run with it"), but the false-positive test results since one of the protein components of the vaccine resembled one of the HIV proteins against which antibodies were produced in vaccinated individuals.

Moreover, there have been talks about the certain resemblance between the spike-protein of the coronavirus and the so-called syncytin protein that could result in antibodies against coronavirus blocking syncytin and leading to infertility. In reality, the resemblance between spike-protein and syncytin isn’t enough to cause the so-called cross-reaction of antibodies. This is also confirmed by the studies on coronavirus infection cases since such cross-reaction can occur with the same rate of success during the naturally acquired infection itself and not during the vaccination per se.

Below I will do my best to gather all the knowledge we have about the different types of vaccines and make certain recommendations given our reality.

Coronavirus vaccines can be divided into four main groups:

1) Nucleic acid-based vaccine – such vaccines contain genetic material –DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) where the instructions on creating viral antigen (protein component of the virus) are encoded. In the case of coronavirus, such antigen is the viral spike-protein. When this genetic material enters human (host body of the virus) cells, the encoded information forces protein synthesis apparatus in the cell to produce antigens of coronavirus, which itself stimulates the immune reaction in the host body.

Such vaccines have the following advantages: 1. They can be developed relatively fast and easily 2. Since the cells in the host body produce antigens in high amounts, the subsequent immune reaction is strong, 3. It doesn’t contain living components and that's why there's no risk of developing a disease.

As for the disadvantages of the aforesaid group of vaccines: 1) Usually requires low temperature for the transportation and storage, 2) Has never received a license for large-scale vaccination roll-out in humans 3) Usually requirs follow-up dosage (so-called boosting).

2) Viral vector (carrier)-based vaccine – Those vaccines also deliver instructions to host cells for the synthesis of viral (in this case, coronavirus) antigen. Unlike the first group of vaccines, this group uses other "harmless" viruses to deliver encoded genetic information to human cells. Adenovirus (the virus causing the common “cold) is primarily used as a "harmless" virus. As a result, human cells start to produce antigens (spike-proteins) of the coronavirus according to the delivered instructions and which in turn stimulates the development of an immune response in a host body.

Such vaccines have the following advantages: 1. This technology has been around for decades 2. It causes a strong immune response, 2. Doesn’t require special conditions for transportation and storage.

As for the disadvantages of the aforesaid group of vaccines: 1) Since adenovirus is widespread among the human population, the host body could have a strong immune defense against the virus decreasing its effectiveness as a carrier-virus 2) It is much more difficult to develop than the nucleic acid-based vaccines and requires more complex technology.

Since the first and second group of vaccines has yet to be used for mass-vaccination of population, there is skepticism as to whether the introduction of genetic information into the human body will have long-term consequences due to the administration of the encoded information in the host body. In this regard, vaccines containing DNA (proportion of vaccines under the first group and practically all vaccines under the second group contain DNA) are particularly noteworthy, since there is a theoretical probability that the DNA introduced to the body will be embedded in the genome of the host body. Processes following such embedment particularly depend on where, which part of the genome, was it embedded. In most cases, it might not have harmful results, however, in some cases, it might cause damage to the gene necessary for the functioning of the human body and in time, could be followed by the development of various diseases (including cancerous processes). Although the probability of practical occurrence of this theoretical possibility may be quite small, in the case of mass vaccination of the population, this probability may reach a significant number.

One more important fact – when describing vaccines containing RNA (and currently, such are licensed Pfizer and Moderna vaccines), it is constantly emphasized that the RNA molecule only acts as a mediator and its sole purpose is to deliver instructions and “transmit” information to human cells; that this molecule is dismantled and destroyed in the cells soon after; that it has no contact with host cell nucleus where human genome (i.e., all genetic information) is stored; that genetic information always flows in one direction: from DNA to RNA and then to protein; that ribosome “translating” RNA into protein is in the cytoplasm and not in the cell nucleus and so on. Therefore, it is safe to say that viral DNA-based vaccines are linked to all the negative effects that RNA-based vaccines lack.

Given all mentioned above, RNA vaccines, considering their mechanism of action, should be considered as less harmful compared to DNA vaccines. Logistically speaking, transportation and storage of DNA vaccines are easier to manage since DNA molecule is more stable than RNA. However, to assess the pros and cons of the vaccine, as mentioned above, it is not enough to consider logistical issues alone, and first, it is vital to consider the long-term outcomes of the vaccine and its impact on the human body.

Therefore, among the vaccine groups developed with new technologies, RNA-containing vaccines appear to be a much safer choice than DNA vaccines.

However, vaccines developed with "traditional" technologies, divided into two main groups (3rd and 4th group of vaccines), should also be a matter for serious consideration:

3) Protein vaccine – such vaccines contain purified particle (subunit) of the virus that can stimulate an immune response in the body without risk of infectious processes because it doesn’t contain the whole virus. Besides the protein subunit, such vaccines can contain polysaccharide molecules or a mixture of both, protein and polysaccharide molecules. However, in the case of a coronavirus, only protein vaccines have been developed so far. Such so-called component (acellular) vaccines have been used in medical practice for a long time now (for example, Hepatitis B vaccine, whooping cough vaccine, and pneumococcal vaccine).

Advantages of the third group of vaccines: 1) Vast practical experience of using this vaccine (including mass vaccination) 2) Long experience in the safety of the vaccine for immunocompromised patients, 3) Infectious processes cannot develop due to the acellular nature of the vaccine 4) relative stability facilitating logistical problems.

Disadvantages of the aforesaid group of vaccines: 1) Developing and manufacturing complexity – thus, less agility and flexibility in terms of mass-production, 2)Requires follow-up vaccination (boosting) and use of adjuvant (molecules that potentiate immune response), 3) Requires work to determine the optimal antigenic combinations, which is time and resource consuming and it might serve as an obstacle in terms of synchronizing with the emergence of new genetic variants of the virus.

Considering the above-mentioned advantages and disadvantages, the group of component (protein) vaccines appears to be the most optimal and safe choice for a large-scale vaccination rollout in a country such as Georgia.

However, the potential of the fourth group of vaccines, produced based on the most familiar and practiced (even “classical”) technologies, should be taken into the consideration:

4) Vaccines containing whole particles of the virus – such vaccines can be divided into two subgroups: 4.1 Live attenuated (“weakened”) and 4.2. Inactivated (killed) vaccines. Examples of live attenuated vaccines that have been used for decades are the measles-mumps-rubella (MMR) vaccine, yellow fever vaccine and as for the inactivated vaccines, examples are seasonal flu and hepatitis A vaccines.      

Advantages of the fourth group of vaccines: 1) Vast practical experience of using this vaccine (including mass vaccination) 2) Ability to stimulate strong immune response 3) Relatively easy to produce 4) Relative stability facilitating logistical problems.

 Disadvantages of the aforesaid group of vaccines: 1) Live attenuated vaccines are counter-effective for immunocompromised patients, 2) In rare cases, it might worsen the existing infectious processes.

Considering the advantages and disadvantages of the fourth group of vaccines, these vaccines also appear to be the relatively safe choice for a large-scale vaccination rollout in a country such as Georgia, albeit given then immediate adverse effects, this group is the most problematic.

The table below presents the list of all vaccines that have reached phase III of trials

Group

Subgroup

Manufacturer

Status

1. Nucleic acid-based

1.1. RNA

Pfizer-BioNTech

Phase III

US (FDA) and EU approved

 

 

Moderna

Phase III

US (FDA) and EU approved

2. Viral vector-based

2.1 ChAdOx1

Oxford-AstraZeneca

Phase III,

Approved in the U.K and India

 

2.2. Ad26, Ad5

Gamaleya

Phase III,

Approved in Russia

 

2.3 Ad5

CanSino

Phase III,

Approved in China

 

2.4 Ad26

Johnson & Johnson

Phase III

3. Containing viral component

3.1 Protein

Novavax

Phase III

 

 

Vector Institute

Phase III

Approved in Russia

4. Containing the whole virus

4.1 Inactivated

Sinopharm

Phase III

Approved in China

 

 

Sinovac

Phase III

Approved in China

 

 

Sinopharm-Wuhan

Phase III

Approved in China

 

 

Bharat Biotech

Phase III

Approved in India

  


Giorgi Kamkamidze,

Doctor-immunologist, Doctor of Medical Science, Professor
Director of the Clinic NeoLab

15.01.2020