There are four types of COVID-19 vaccines part 6

How do whole virus vaccines trigger immunity?

Both live attenuated and inactivated vaccines contain the whole or part of the disease-causing pathogen, but the type of immunity they trigger is slightly different.

Live attenuated vaccines are derived from viruses that have been weaked under laboratory conditions, so that when injected they will infect cells and replicate but cause no or only very mild disease. They may be unsuitable for people with compromised immune systems (e.g. those with HIV) and pregnant woman though, because even in a weakened virus may trigger disease in vaccinated individuals or their contacts. This has been for vaccine derived poliovirus associated with the oral vaccine.

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There are four types of COVID-19 vaccines part 5

Advantages and disadvantages of inactivated virus vaccines :

  • Well-established technology
  • Suitable for people with compromised immune systems
  • No live components, so no risk of the vaccine triggering disease
  • Relatively simple to manufacture
  • Relatively stable
  • Booster shots may be required

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There are four types of COVID-19 vaccines part 4

Advantages and disadvantages of live attenuated vacciness:

  • Well established technology
  • Strong immune response
  • Immune response involves B cells and T cells
  • Relatively simple to manufacture
  • Unsuitable for people with compromised immune systems
  • May trigger disease in very rare cases
  • Relatively temperature sensitive, so careful storage necessary
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There are four types of COVID-19 vaccines part 3

What are whole virus vaccines and how could they be used against COVID-19?

Whole virus vaccines use a weakened (attenuated) or deactivated form of the pathogen that causes a disease to trigger protective immunity to it. There are two types of whole virus vaccines. Live attenuated vaccines use a weakened form of the virus, which can still grow and replicate, but does not cause illness. Inactivated vaccines contain viruses whose genetic material has been destroyed by heat, chemicals or radiation so they cannot infect cells and replicate, but can still trigger an immune response.

Both are tried and tested vaccinated strategies, which form the basis of many existing vaccines – including those for yellow fever and measles (live attenuated vaccines), or seasonal influenza and hepatitis A (inactivated vaccines). Bacterial attenuated vaccines also exist, such as the BCG vaccine for tuberculosis.

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There are four types of COVID-19 vaccines part 2

The four main types of COVID-19 vaccine

There are four categories of vaccines in clinical trials: 

  • Whole virus
  • Protein subunit
  • Viral vector
  • Nucleic acid (RNA and DNA)

Some of them try to smuggle the antigen into the body, other use the body’s own cells to make the viral antigen.

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There are four types of COVID-19 vaccines part 1

There are more vaccine candidates simultaneously in the pipeline for COVID-19 than ever before for an infectious disease. All of them are trying to achieve the same thing – immunity to the virus, and some might also be able to stop transmission. They do so by stimulating an immune response to an antigen, a molecule found on the virus. In the case of COVID-19, the antigen is typically the characteristic spike protein found on the surface of the virus, which it normally uses to help it invade human cells.

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COVID-19 vaccine development part 22

How to protect ourselves and others:

  • Stay home and self-isolate
  • Clean hands frequently 
  • Cover your mouth and nose
  • Avoid touching
  • Maintain a minimum physical distance of at least 1 metre from other
  • Stay away from crowd
  • Use a medical mask
  • Regularly clean and disinfect

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COVID-19 vaccine development part 21

Resources on COVID-19 vaccines development:

  • WHO target product profile for COVID-19 vaccine
  • Vaccine landscape
  • Solidarity vaccine trial
  • Access to COVID tools (ACT) Accelerator
  • COVAX facility (WHO) Covax explained (GAVI) COPVAX (CEPI)
  • WHO guidance on ethnics of vaccine allocation
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COVID-19 vaccine development part 20

Working together to deliver vaccine to all countries:

  • The Access to Covid-19 Tools (ACT) Accelerator was launched in April 2020 to speed up development and delivery to countries of diagnostics, treatments and vaccines. It includes a health systems connector to support delivery of these resources to countries.
  • WHO developed a framework for equitable  and affordable access to safe and effective vaccines.
  • The COVAX facility is an umbrella mechanism through which demand and resources are pooled to support procurement of, and equitable access to, COVID-19 vaccines.
  • The ACT Accelerator aims to deliver two billion vaccine doses for global needs by the end of 2021.
  • Vaccine allocation will be driven by public health needs for priority groups, which may represent about 20% of the population, in the first year.
  • Countries will be asked to develop vaccination plans.
  • WHO recommends front-line personnel (such as health workers) and seniors be the first priority to receive vaccine
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COVID-19 vaccine development part 19

WHO Solidarity vaccine trial (Achieving rapid progress towards global objectives) :

  • Evaluating several different candidate vaccines:

      Increasing the likelihood of finding several effective vaccines

  • Expenditiously enrolling people at sites with high rates of COVID-19:

      Rapid accumulation of data to support rigorous evaluation

  • Eliminating inefficiency of design and conduct of separate trials:

     Results within 3-6 months after each vaccine is ready for inclusion

  • International collaboration and country commitment:

      Fosters international deployment with equity of access

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