Amid the global risk of new coronavirus variants, the government encouraged Idul Fitri mudik (exodus) travelers to get booster shots before departing. People who had received a third shot could skip certain health protocols on their trips, and in many places booster doses were readily available. The government had thought its new travel policy would significantly increase booster coverage.

However, as of May 3, the COVID-19 booster rate stood only at 19.39 percent of the targeted population, some 208.26 million people, Health Ministry data shows. This low rate can be attributed, in part, to public hesitancy to get another vaccine dose.

The booster vaccine is strongly recommended for the general public, especially the elderly and other vulnerable groups. Many studies have revealed that the protection of a double-dose COVID-19 vaccine regimen wanes over time.

Pulmonologist Erlina Burhan of Persahabatan Hospital in Rawamangun, East Jakarta, said that the effectiveness of COVID-19 vaccination typically decreased within six months of the second administration. These findings, she added, had prompted the government to offer COVID-19 booster shots to enhance protection.

“Vaccines reinforced by a booster can prevent hospitalizations and deaths from severe illness caused by COVID-19 infection,” Erlina said at a roundtable discussion titled “Understanding COVID-19 Vaccine Effectiveness” on April 27.

Held by the Southeast Asian Ministers of Education Organization (SEAMEO), the Thai TROPMED Network and the Philippine College of Physicians, the discussion reviewed newly released data that suggested the world’s most administered vaccines – AstraZeneca’s viral vector vaccine and the available mRNA COVID-19 vaccines, which include the Pfizer vaccine – offer the same protection from the coronavirus.

Erlina is one of 18 infectious disease experts from Asian countries who reviewed the data from VIEW-hub. Developed by the Johns Hopkins Bloomberg School of Public Health and the International Vaccine Access Center (IVAC), the online interactive platform presents data visualizations on vaccine use and impact. The platform is updated on a weekly basis to include real-world studies on the effectiveness of vaccines.

Released on April 25, the report entitled A Southeast Asia Expert Review of Global Real-World Vaccine Effectiveness Against SARS-CoV-2 examined 79 real-world studies. These included comparative studies on the outcomes of two most widely used types of vaccines, AstraZeneca’s viral vector vaccine and mRNA vaccines, especially BNT162b2 and mRNA-1273.

Erlina said the new study clarified that AstraZeneca’s viral vector vaccine and available mRNA vaccines could protect people from hospitalization in 91.3 to 92.5 percent of cases and death in 91.4 to 93.3 percent of cases, with no statistical difference between the two classes of vaccine.

The data provided by the IVAC for the experts’ review used studies evaluating Delta and previous SARS-CoV-2 variants only. But the latest statistics show that both types of vaccines also provide comparable protection against the highly contagious Omicron variant.

“AstraZeneca’s vaccine and the available mRNA COVID-19 vaccines both consistently deliver high protection, even in more vulnerable groups such as those who are aged 60 years and above,” said Erlina, a pulmonary specialist from the Pulmonology and Respiratory Medicine Department of the University of Indonesia (UI) School of Medicine.

Although initial antibody response numbers produced by COVID-19 vaccines vary, they are not a good predictors of how effective a vaccine will be in preventing hospitalization and death from serious illness.

Citing an excerpt of the experts’ review, Rontgene Solante of the Philippine College of Physicians said antibody profiles could not accurately represent the full immune response over time and were not effective predictors of vaccine effectiveness against severe disease. The team of experts strongly supported considering vaccine effectiveness against severe COVID-19 outcomes, he added.

“This is a more relevant metric of vaccine performance, particularly during the current Omicron variant wave when infection rates are high in both partially and fully vaccinated individuals,” said Solante, an infectious disease expert.

A team of experts from Thailand found in their studies much higher initial antibody spikes following a dose of the the Pfizer mRNA vaccine than the AstraZeneca vaccine or CoronaVac vaccine. But the two vaccines were equally effective against hospitalizations and death. This conclusion was based on the results of a COVID-19 study conducted simultaneously in the Thai cities of Chiang Mai, Kalasin, Bangkok and Phuket.

In Chiang Mai, both the AstraZeneca vaccine and the Pfizer mRNA COVID-19 vaccine provided equivalent protection against serious COVID-19 outcomes. This was true when they were used as primary series or as a booster.

In Kalasin, the impact of Omicron and the importance of the booster dose were particularly apparent. The study found that both the AstraZeneca and Pfizer primary vaccine series were less than 15 percent effective before the booster dose.

“Vaccine choice should not be determined by initial antibody response but rather by effectiveness against the most severe consequences of COVID-19,” said Sunate Chuenkitmongkol, deputy director for scientific affairs at the Thai National Vaccine Institute.

It is likely that public booster hesitancy comes from a poor understanding of its importance. Some people may feel they are safe enough after two doses. Others say they cannot find a booster vaccine of the same type as the primary series they received.

In response, Erlina said that in areas that had limited resources or faced logistical challenges, such as poor storage facilities, one of the most effective ways to achieve booster vaccine targets was to use any available booster vaccine. A viral vector vaccine could be considered because of its comparable effectiveness to mRNA vaccines and its simpler distribution system.

There is no choice but to optimize COVID-19 booster vaccinations to better protect the Indonesian public. Being too picky about booster shots risks missing out on protection against the serious impacts of the virus.

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The author is a staff writer at The Jakarta Post.