THE country’s Health Technology Assessment Council (HTAC) has already recommended the administration of a fourth dose or Booster Shot Number Two to the immunocompromised population 18 years old and above. Immunocompromised are those receiving cancer treatment or immunosuppressants, and also those with advanced or untreated HIV infection, among others.
Approved Covid-19 vaccines for the second booster were AstraZeneca, Sinovac, Pfizer-BioNTech, Moderna, and Sinopharm. A lot of noise was created to expand the second booster coverage to include health-care workers, the elderly, and overseas foreign workers. However, the recommendation was for the government to expand first the coverage of the primary series doses across the priority groups.
So, is a second booster dose really needed?
So far, a total of 148,383,339 Covid-19 vaccines have been administered as of May 16, 2022, where 68,710,521 have completed their doses as of the same date, while 13,650,414 received their first booster dose also as of the same date.
During one of the “Stop Covid Deaths” webinar by the University of the Philippines, in partnership with UP Manila NIH National Telehealth Center and in cooperation with UP Philippine General Hospital, titled “Isa pa nga: Kailangan ba talaga ang 2nd Covid-19 Booster?,” Dr. Marysia Recto, immediate Past President of the Philippine Society of Allergy, Asthma and Immunology (PSAAI), Department of Pediatrics of the UP Philippine General Hospital, pointed to the recommendation of World Health Organization (WHO) Director General Dr. Tedros Adhanom Ghebreyesus regarding vaccines, who said that it is still one of the most important tools in preventing outbreaks and keeping the world safe. “But we have to realize that there is still a lot of vaccine inequity, either through hesitancy or lack of availability,” she said.
Fast-tracking vaccine development
As a pediatrician, Dr. Recto knows how important vaccines are in controlling many diseases and vaccination has been around for many decades. She said that the conventional pathway to vaccine development takes years in order to establish efficacy, safety and immunogenicity. “The Covid-19 vaccines are unprecedented because of the need of the times, that we have to control a disease that is potentially deadly.”
Vaccine development for Covid-19 was really fast tracked mainly on knowledge that has been done through years of technology that is now being applied. “Up to now, we are still observing the effects of Covid-19 vaccination.”
Last year, Dr. Recto said the concern was more on efficacy of the vaccines but as they are being used, the effectivity of the vaccines really showed as the number of severe and critical cases significantly dropped, which led to the opening of several economies in the world, including ours.
Waning immunity
But now the concern is “waning immunity.” A study done in Israel, one of the first countries to achieve almost full vaccination of their population, noted that 10 weeks after the second shot, immunity really waned. But experts there have not yet determined what antibody level would say that there is no more protection or the “correlate of protection.”
When the Delta surge came, about the time that Israel was done with their second shot, they had to administer the third, or the first “booster” shot. “They found that indeed, the antibody levels have started to rise again. It may not have gone as high as during the second shot, but then, it started going down again, and they were faced now with the Omicron surge.”
Because of Israel’s ability to vaccinate more, they embarked on the fourth shot or the second booster. Based on Israel’s experience, a lot of countries are looking at them, including the country’s own Department of Health, which gave its recommendation based on Israel’s studies. But is it applicable to the Philippine setting?
Vaccinology 101
The primary response, which can be one, two or three shots depending on organism being tried to control, helps provide a boost or generate a certain antibody level in the blood. But the antibody levels are known to wane because it is degraded by the body’s system, Dr. Recto explained. That means sometimes, there really is a need for a booster in order to provide a heightened and more sustained immune response. “Vaccines contain many elements that work together that generate a synergistic effect, the perfect team of antibody and T/B responses to generate vaccine immunity.”
Going back to the principle of vaccine boosters, Dr. Recto said after the first vaccination comes the primary response, which can wane with time, while the second vaccination will induce a stronger and larger immune reaction, that’s why it’s called the “primary series.” But the second shot has been found to have waning antibody levels so is a booster needed? With the third shot, there was an increase again but there was still a dip in the antibody levels, so this brings the concern about the fourth shot or the second booster.
Is there really a need for a second booster?
There are several considerations but when making recommendations, Dr. Recto said evidence should be strong enough to determine the objective which is—is it disease prevention or efficacy against severe disease? There’s also the issue of whether boosters can address and prevent new variants, proper boosting and timing, the need to look at “science over politics,” or the issue of pushing a vaccine agenda and finally, herd immunity, which cannot be achieved without vaccine equity.
She said the decrease in vaccine protection over time appears to be real for all forms of infection starting from the 6th month after the second injection but does not appear to have a real impact on the risk of Covid-19-related hospitalization or death. Also, lowering of protection is more evident in elderly people (65 years and above) and in those at higher risk of Covid-19. However, although the usefulness of a booster is still being debated, it is recommended in a number of countries for the elderly and those at higher risk of contracting severe disease.
But Dr. Recto added that future data on vaccines’ duration of protection and real-life efficacy and safety of booster doses will add evidence on its hypothetical interest in the population.
“However, the priority is to vaccinate all eligible individuals not yet vaccinated with the recommended dose regimen so we can go for herd immunity,” Dr. Recto concluded.
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