How Effective are COVID-19 Vaccines?

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Effectiveness of the mRNA COVID-19 Vaccines

The United States CDC released information on 7 June 2021, regarding their study of the effectiveness of vaccines in fully vaccinated people.

The main information was that mRNA COVID-19 vaccines reduced the risk of infection by 91% for fully vaccinated people.
This means that 90 out of every 1,000 fully vaccinated people can still be infected.

Next, it showed that with the vaccinated study participants who became infected with COVID-19, the virus was 40% less detectable in their noses.

The report stated “While these indicators are not a direct measure of a person’s ability to spread the virus, they have been correlated with reduced spread of other viruses, such as varicella and influenza.

Looking at those figures, it looks like 90 out of every 1,000 fully vaccinated people can still catch COVID-19.
But only about 40% of that 90, ie: about 36 people, would still be able to transmit the vaccine to others.

Therefore mRNA COVID-19 vaccines reduced the risk of transmitting the infection to others by 96.4%.

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A reasonably good result, although not perfect.

Fully vaccinated people still need to be careful, as they may be one of the few that can still be infected, and give the virus to loved ones or strangers.


Pfizer-BioNTech and Moderna are the mRNA COVID-19 vaccines.

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  1. If you feel like sending $5 to buy me a cup of coffee, please click the donate button.

  2. An August report from the US Centers for Disease Control and Prevention (CDC) showed that following large gatherings in a town in Massachusetts, 74% of 469 new COVID-19 cases that occurred were in fully vaccinated people, (46% Pfizer, 38% Moderna and 16% Janssen). Most people in the location (69%) were fully vaccinated.
    89% of the cases that were sequenced were identified as Delta.
    Of the five COVID-19 patients who were hospitalised, four were fully vaccinated.

    4 of the 346 fully vaccinated were hospitalised. Two of these had underlying medical conditions.
    1 of the 123 not vaccinated or not fully vaccinated was hospitalised.

    464 infected cases did not need hospitalisation.

  3. A later CDC report has shown that immunocompromised people, who have been fully vaccinated, have accounted for a large proportion of hospital breakthrough cases (40-44%).
    With such a high rate of hospitalisation, (40-44%), from the 3% of the U.S. adult population that are immunocompromised, it is important for them have booster doses of the vaccine.

    The report also noted that immunocompromised people who are infected with SARS CoV-2 are also more likely to transmit the virus to household contacts.

    An Australian report also shows that people who are immunocompromised may need extra doses of some vaccines to optimise protection.

    Being ‘immunocompromised’ means having a weakened immune system due to a medical condition or treatment. Many conditions can cause immunocompromise, including:

    • Cancer, especially blood cancer (leukemia or lymphoma).
    • Treatments for cancer (e.g. chemotherapy, targeted therapies, radiotherapy and CAR-T cell therapy) can also weaken the immune system.
    • Having a bone marrow, stem cell or solid organ transplant.
    • Immune deficiencies.
    • HIV infection (particularly if the CD4 count is low).
    • Taking medications that weaken your immune system. These medications are called immunosuppressants or immunomodulators.

    Source PDF File:

    Vaccination protects you from having severe illness and needing to go to hospital as a result of getting COVID-19.

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