Vaccine effectiveness

  • by VaccineHealthCenter

Vaccine effectiveness refers to how well a vaccine works when used in the natural environment. In other words, it is the indicator of the vaccine’s ability to prevent the outcomes of interest in the ‘real world.’ In establishing how effective the vaccine is, health agents and researchers monitor the new disease cases in two groups, the vaccinated and the unvaccinated fellows. Unlike vaccine efficacy that tries to determine how well the vaccine works in the most favorable (controlled) conditions, vaccine effectiveness follows the worthiness of the vaccine on the population that's not under control. The real-world population and not the trial volunteers are used for vaccine effectiveness.

Why is vaccine effectiveness a critical parameter?

the government and health organizations would not waste money on some scrappy stuff in the name of vaccine effectiveness. Consequently, it implies that vaccine effectiveness is an essential index in the health sector for a vaccine candidate of interest. Here are the primary reasons behind a vaccine effectiveness determination;

  • Establishment of the disease burden; the data obtained through vaccine effectiveness is used to determine the impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators. In calculating the disease burden of infection, data on the compromise of life quality and disability of years is compared to vaccine effectiveness. If a vaccine has a high effectiveness rate, it promotes immunization, sustained vaccine uptake, development of better vaccines, and more research in vaccines.
  • Determining the cost-effectiveness factor; the data on vaccine effectiveness is also critical in establishing the pivotal point for the cost of disease against the cost of vaccination. At any point in time, the vaccine cost determines the effectiveness of the initiating program. This is because, the greater the burden of disease, and the greater the proportion that is vaccine-preventable, the more cost-effective a program will be.
  • Telling the effectiveness and the efficiency of vaccine efficacy; while vaccine efficacy is determined in controlled conditions before the vaccine candidate is dispatched to the public, vaccine effectiveness is established in the typical natural conditions once the vaccine is out in the market for the population. The data on vaccine effectiveness is then compared to the vaccine efficacy data. Depending on the deficit, the researchers can tell how effective and efficient the vaccine efficacy data was.
  • Establishing the direness of clinical trials: besides featuring the effectiveness of the vaccine efficacy data, vaccine effectiveness tells how critical clinical trials are in the developmental stages of a vaccine. Although there normally occurs discretion and disparity between the two parameters, the deficit is still crucial for the purposes of research.
  • influencing policy and program decisions of a nation; some of the policy and the program decisions made by heads of states partly depend on the data from vaccine effectiveness initiatives. Whether a government will or will not support a policy or a program binding agreements with a given health agency may depend on how effective the vaccine (and other health products offered by that agency) was.

Factors affecting vaccine effectiveness
Although vaccine effectiveness is a critical health indicator valued by organizations, governments, the public, and health agencies, many mitigating factors influence the final outcome. Here are the tenets that influence the vaccine effectiveness;

Host factors

These are the characteristics of the vaccine recipient that determines how effective the vaccine will be. Age is one such factor. Most vaccines will work well on mid-aged people, and not the young children or seniors. There could be co-morbidities that make a recipient more susceptible to the disease despite the vaccine. On the other hand, a person with prior exposure to the disease may have natural immunity against the disease even without the vaccine.

Logistic issues

These issues include cold chains, administration bureaucracy, and compliance to the vaccine schedule. An administration that subjects the patients to long chains of unnecessary procedures may discourage the patients, making them lose hope and miss out on the vaccine. Besides, if such conditions move the patients into not complying with the vaccine schedule (for the vaccines received more than once), the effectiveness of the vaccine will be largely impacted as such vaccines may only be effective with the completion of the dosage.

Epidemiological factors

Disease factors like herd immunity, mismatch with circulating strains, the emergence of new viral/bacterial variants, and the strength of infection also affect how effective a vaccine can be. Most of the viruses and bacteria keep mutating and before the doctors can tell it, the vaccine providers could only be vaccinating the patient for a mismatched variant. Additionally, if an infection is so strong, it could overpower the vaccine, especially if the patient suffers from other medical conditions.


Health agencies must tell how effective a vaccine is on a population. This is because this parameter is important in rating the effectiveness of vaccine efficacy data and determining health policy and program decisions, among other critical essences. However, the vaccine effectiveness faces many challenges just like vaccine efficacy, making it hard for the data on effectiveness to be entirely true. The factors that influence how effective the vaccine can be are related to the host, logistic issues, and epidemiological issues.