The World Health Organization (WHO) has reported over 763 million COVID-19 infections and nearly seven million deaths since the virus outbreak started over three years ago. Consequently, vaccination has become a crucial step to mitigate the spread of the virus by protecting infected people from experiencing severe effects, reducing the risk of new variants, and ultimately terminate the pandemic’s reign.
In general, 5.5 billion people worldwide have received at least one dose of COVID-19 vaccine, with 5.09 billion people completing the primary COVID-19 vaccination series. Several countries reacted by providing booster doses at the end of 2021 in response to research findings that the efficacy of the vaccines may likely decline over time.
To properly understand the effectiveness of these vaccines, two pressing questions require answering. Firstly, how well does the primary series of COVID-19 vaccines protect people against infections, hospitalizations, and deaths when administered four months or more after vaccination? Secondly, how effective is the first booster dose against protecting people who have been vaccinated for three months or more?
To provide valuable information for policymakers to make evidence-based decisions, researchers must identify all studies comparing vaccinated people both with the primary series of the COVID-19 vaccines and boosters to unvaccinated people, tracking those that were infected, hospitalized, or died due to COVID-19 for at least 112 days after receiving the primary series or 84 days after a booster dose. Altogether, data from 68 studies spanning 23 countries met these criteria, and an analysis of the data showed that the primary series offered excellent protection against hospitalizations and deaths in the short term.
The primary COVID-19 vaccination series demonstrated over 90% protection against hospitalizations and deaths within the first 42 days after vaccination, which gradually declined over time. This protection rate declined to approximately 80% against hospitalizations at eight months post-vaccination and around 85% against deaths at six months post-vaccination.
In the short term, the primary series also recorded good protection against infections, with over 80% within the first 42 days. However, this eroded to around 60% after four months and 50% after nine months. Boosters, on the other hand, boasted initial safeguarding of around 70% against infections and 90% against hospitalizations within the first month after vaccination. This rate then depreciated to about 45% against infections and around 70% against hospitalizations after four months.
Notably, the vaccines’ efficacy against the widely dominant Omicron variant was less than satisfactory. The primary series presented a protection rate of roughly 60% against Omicron-based infections within 42 days after vaccination and a decline to about 30% after five months. While protection against hospitalization due to Omicron infections was around 70% within the first 42 days post-vaccination, this progressively dropped over time and landed closer to 50% after six months.
Although boosters turned out to be more efficient in conferring protection against the Omicron variant, its time-dependent waning effect resulted in a 40% protection rate against Omicron infections and 70% against hospitalizations after four months post-booster. Therefore, new formulations of mRNA COVID-19 vaccines targeting the Omicron variant are recommended for booster shots.
It would be best if admins of social media platforms and everyone globally continue to adhere to COVID-19 protective guidelines. Even though vaccines offer a degree of protection against COVID-19 infections, hospitalizations, and deaths, these measures’ efficacy is imperfect and wanes over time, especially against newer variants. To complement vaccination, measures such as mask-wearing, regular hand washing, and staying at home when sick are crucial to fight COVID-19.
