Booster doses are administered to vaccinated individuals who have completed a primary vaccination series-currently one or two doses of COVID-19 vaccine depending on the type of product.
The objective of a booster dose is to restore vaccine effectiveness from that deemed no longer sufficient.
Why Booster Doses?
The common primary goal of vaccination in the COVID-19 pandemic remains to safeguard against hospitalization, serious disease, and death. Thus, booster doses may only be required if there is evidence of limited protection against these disease outcomes over time.
The extent of the waning of immunity and need for booster doses of vaccine may vary between the various vaccine products, target populations, circulating SARS CoV-2 virus, in particular variants of concern (VoC), and power of the exposure. For some vaccines, restricted booster indications have been incorporated into the product label of some jurisdictions.
In the current period of continuous global vaccine supply, shortage equity deliberations at country, regional and global levels remain an important consideration to ensure vaccination of high priority groups in every region. Enhancing coverage of the primary vaccination series should be made a priority over booster vaccination.
Factors to consider for Covid19 Booster Jab
- Dwindling Immunity
Neither immune protection nor the duration of the protection has been ascertained to date. A study suggests the correlation between the efficacy of various vaccines against symptomatic disease and neutralizing antibody titers induced by those vaccines in the short term but it is unclear if declining titers over time since vaccination are indicative of declining vaccine effectiveness, especially against VoCs.
Even though the information on the immunogenicity of some vaccines implies that antibodies would last for at least 6 months, the waning of neutralizing antibodies has been documented. Although there may be a loss of protection against infections by SARS-CoV-2, protection against severe illness is more durably conserved due to anamnestic humoral and cell-mediated immunity.
- Global vaccine supply and national equity
The national vaccination programme policy decision to add a booster dose would take into account the strength of evidence regardings the need for these doses, their safety, their effectiveness, as well as the global availability of vaccines.
Giving booster doses to a large proportion of a population when a lot of people are yet to receive even a first dose may undermine the principle of national and global equity. Prioritizing booster doses over speed and breadth in the initial dose coverage may also damage the prospects for global mitigation of the pandemic, with severe implications for the health, social and economic well-being of people globally.
- Efficiency of vaccine
Studies on the period of protection are observational studies. Even though they are often difficult to interpret due to some confounding factors, developing data always show a decrease in vaccine effectiveness against infection and milder forms of COVID-19 over time.
Concerning the length of safety against disease requiring a home, current data show an overall continued high level of effectiveness, although data differ across age groups, target populations, and products. A vast majority of current infections are identified in unvaccinated populations.
In conclusion, Introducing booster doses should be strongly evidence-driven and targeted to the population groups who are in the greatest need. The rationale for executing booster doses should be guided by evidence on waning vaccine effectiveness, in particular a decrease in protection against serious disease in the general population and high-risk populations, or due to a circulating VoC. The major focus should remain on urgently improving global vaccination coverage with the primary series driven by the aim of protecting against severe disease.
Individuals should be encouraged to maintain safety protocols and Order a Covid-19 Home Test should they have any of the symptoms of Covid19.