COVID-19 vaccine booster shots made from the original strain of the virus still save lives among vulnerable Indonesians, but provide limited protection for the wider public, according to a new study by OUCRU Indonesia, Universitas Gadjah Mada, and the U.S. Centers for Disease Control and Prevention.
These vaccines were developed based on the original SARS-CoV-2 strain found in Wuhan, before newer variants such as Omicron emerged. The study found that, for adults over 50 and those with underlying health conditions such as diabetes, heart disease, or lung problems, third and fourth booster doses of these vaccines continued to prevent hospitalisation and death more than a year after vaccination.
The study also found that these boosters no longer stop otherwise healthy people from catching the new Omicron variants. This is likely because protection fades over time and the virus has evolved to be better at evading immunity.
A third-dose booster (given around 20 months prior to the study) reduced the risk of hospitalisation by about 38 percent and death by about 55 percent among adults over 50 years of age. It also lowered the risk of death by roughly 55 percent among people with one or more chronic conditions.
A fourth-dose booster (given around 13 months prior to the study), reduced the risk of hospitalisation by about 50 percent among older adults and by 74 percent among people with one or more chronic conditions.
The study was conducted across 14 hospitals, laboratories, and community health centres in the cities of Jakarta and Yogyakarta, Indonesia, and followed more than 2,000 adults between March 2023 and May 2024.
Nearly all infections during this period were caused by Omicron XBB or JN.1, the dominant variants circulating in Indonesia at the time. The vaccine boosters were mostly mRNA vaccines such as Moderna and Pfizer, given after primary vaccination with either inactivated vaccines (CoronaVac) or viral vector vaccines (AstraZeneca).
“The Indonesian government declared the end of the pandemic in June 2023 and, as in many low- and middle-income countries, has discontinued the booster programme,” said Dr. Bayu Satria Wiratama, researcher at Universitas Gadjah Mada and first author of the paper. “Nonetheless, our findings show that these boosters still make a real difference for older adults and people with health conditions.”
“The findings of this study make a compelling case for sustained revaccination strategies, even in settings where public health resources are limited,” said Assoc. Prof. Raph Hamers, researcher at OUCRU Indonesia and senior author. “Continued research is needed to track the long-term durability of protection from the currently used vaccines, which are based on the Wuhan strain, in Indonesia and other nations. This includes defining minimal intervals for boosters and assessing the added value of introducing updated vaccines, which are not currently in use in Indonesia.”
The study was led by researchers at Universitas Gadjah Mada and OUCRU Indonesia, in collaboration with the Indonesian Ministry of Health, with support from hospitals, laboratories, and community health centres across Jakarta and Yogyakarta. It received funding from the U.S. Centers for Disease Control and Prevention.
The paper is accessible here.