Benefits and Harm of Vaccination Against Covid-19

Benefits of Vaccination Against Covid-19

(1) Exposed to a new infectious agent, vaccination is a key intervention that can limit the emergence and spread of a novel pathogen. This is because elimination or control of infections will reduce the number of susceptible individuals in a population who could become infected with the novel virus.

As a result, if an infected person becomes symptomatic they are less likely to spread the pathogen to susceptible individuals. This effect can be achieved by vaccinating large numbers of people in contact with an infected person.

(2) Vaccination is also effective against emerging infectious diseases because it has been shown that pre-exposure vaccination of children provides indirect protection to unvaccinated adults.

Exposed contacts are less likely to become infected if they are vaccinated because of the reduced number of susceptible hosts. These individuals are not only protected from infection but also through herd immunity, are less likely to transmit the infection to others in their community.

(3) Vaccination may also play an even more important role during epidemics due to its effect on epidemic growth rates. In the case of a large epidemic, when vaccination is introduced it reduces both the number of secondary infections caused by an infected individual and also shortens the duration that they are infectious.

This in turn decreases the number of susceptibles becoming infected in a given amount of time. Therefore infection prevalence curves become steeper as vaccine coverage increases, which ultimately reduces the epidemic size.

(4) As vaccination coverage increases, the duration required for an epidemic to burn out (reached when half of the susceptible population is infected) becomes shorter. This occurs because it takes fewer secondary cases to infect a certain proportion of the population.

For example, if vaccination reduces secondary attack rates by 80% and the initial prevalence is 10%, then it will take 14 cases for an epidemic to reach the endpoint (assuming all secondary cases die, which is a very good assumption). However, if vaccination reduces secondary attack rates by 90% and the initial prevalence is 10% then only 12 cases are required to infect half of the population.

(5) In addition to directly reducing transmission of infection, vaccination may also indirectly reduce transmission. This stems from the fact that fewer infectious individuals will be available to transmit the pathogen to others in their community who are unvaccinated or not adequately vaccinated. Therefore as coverage increases, an even larger proportion of the susceptible population will be indirectly immunized and protected against future epidemics.

(6) Vaccination can also have significant effects on the sizes of future epidemics. If vaccination coverage is maintained at high levels, then the size of any future epidemic will be greatly reduced because there are fewer susceptibles in the population. This effect occurs regardless of whether a new pathogen emerged or an old pathogen re-emerged due to conditions that favored pathogen spread.

(7) Vaccination can limit the size of epidemics because it creates ‘herd immunity’ (I). There are three ways in which vaccination and herd immunity can reduce epidemic sizes: (I-) nonvaccinated individuals may be indirectly protected through reduced transmission rates;

(ii) vaccinated individuals who become infected develop milder symptoms and are less infectious;

(iii) vaccination creates a larger number of immune individuals, which reduces the probability that an infected individual will come into contact with susceptible individuals

(8) Vaccination also limits the size and duration of epidemics by directly reducing attack rates. Because vaccinated individuals develop milder symptoms and are less infectious they contribute to the immune pool by transmitting the pathogen to fewer individuals. In addition, infected vaccinated individuals develop immunity faster and therefore recover from infection more rapidly than their unvaccinated counterparts. This allows treatment of a greater proportion of infected individuals over time which reduces attack rates during an epidemic.

(9) Vaccination may have a significant effect on the size and duration of epidemics by reducing the proportion of susceptible individuals in a population, and subsequently slowing epidemic spread.

This effect occurs because an infected vaccinated individual does not transmit the infection to other individuals who are either vaccinated or already immune due to previous infections. An example of this phenomenon is the case when vaccination reduces the effective reproductive number (R) such that R<1.

In order to determine which of these factors have the greatest impact, a numerical simulation model was developed that incorporated all of the aforementioned effects. The figure below demonstrates how each factor can affect epidemic trajectories under different conditions.

In this analysis, vaccine coverage levels ranged from 0% to 100%; disease mutation rates ranged from 0-2% per year; pathogen death rates ranged from 0-100% and were dependent upon disease type; secondary attack rates for individuals who became re-infected with the same strain varied between 5-95%; vaccine efficacy was set at 75%; and finally, it was assumed that vaccination could indirectly reduce transmission of infection by 80%.

Disadvantages of covid 19 vaccine:

1. This vaccine is not effective against flu strains that have mutated to a different strain after the vaccine was made. In other words, people can get the flu despite being vaccinated for it because the virus has mutated into a new form which this flu shot does not cover.

2. Even if no mutations occur, vaccinating some portion of the population might not prevent epidemics. If the vaccine is only 50% effective and the population has 100,000 members, it means that after an epidemic you would expect around 50,000 cases (preventing them from spreading to other people), but there could still be another 100,000 cases of flu since they were never vaccinated in the first place.

3. Because this vaccine is made from fragments of the virus, it may still induce immunity against other strains that are similar to the ones in the vaccine. This means that after you get vaccinated for one strain (let’s say H1N1), there is a chance that you could become immune to other strains like flu H7N9 or flu H5N1. Not a good thing to have, all it takes is one mutation in the virus and you become “useless” against multiple strains.

4. This vaccine cannot be grown in eggs or fertilized chicken embryos due to mutations that occur with these hosts. Chicken embryos are the preferred host for flu vaccines because they allow the use of eggs as a substrate. This means that you cannot produce vaccines cheaply and quickly, but instead have to rely on egg-based technology which is slower at producing the vaccine.

5. The vaccine must be refrigerated and requires a temperature between 36°F to 46°F or else it would not be effective. If the vaccine is too cold, it won’t work as intended, but if it’s too warm then you’ll have a small incubation period before symptoms start appearing. Both of these conditions will give people the impression that the vaccine failed to protect them against the flu, further reducing confidence in current vaccination methods.

Which covid vaccine is best:

vaccines provide a weakened or dead version of a virus. By introducing your body to a part of the invader, it builds up antibodies and immunity towards them

the covid vaccine makes you more vulnerable to infection from other flu strains because this shot only protects against certain flu viruses. If the virus mutates, then having been vaccinated can actually make you more vulnerable to the effects of that mutated strain.

the vaccine is still being tested – so not only is it an unknown quantity but having side-effects associated with flu vaccine cannot be ruled out.

Who should not take the covid vaccine:

the covid vaccine is not recommended for people who have a history of severe allergic reactions to flu vaccines, or any of its ingredients.

the covid vaccine may cause problems with the electrical activity of the heart in some individuals, including those that are predisposed to such conditions or suffering from other risk factors.

cyclophosphamide is also used in the treatment of lymphomas (Hodgkin’s and non-Hodgkin’s), leukemias, multiple myeloma,

as well as solid organ transplant recipients to prevent organ rejection.

cyclophosphamide is also known to cause bladder side effects such as blood in the urine. Other cyclophosphamide side effects may include urinary tract infections, fever or chills, kidney problems, pneumonia, and nausea.

cyclophosphamide side effects may also include diarrhea, loss of appetite, tiredness, dizziness, and headache.

swine flu is one of the most common strains of influenza A virus that circulates in humans. The swine flu virus is an H1N1 influenza virus that is responsible for causing the 2009 pandemic.

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