In the Philippines, vaccination coverage continues to be a challenge considering the archipelagic nature of the country, where bringing vaccines in far-flung areas in the provinces continue to be a monumental task.
The government, however, is doing everything it can to increase coverage, and continues to embark on a massive awareness campaign that focuses on the vaccines’ safety and effectivity against the virus and even against its variants.
Just recently, a new study on the effectiveness of Covid-19 vaccines was presented. The study accessed the respected International Vaccine Access Center (IVAC) Vaccine Information and Epidemiology Window (VIEW) Hub global database, an online, interactive map-based platform for visualizing data on vaccine use and impact and maintained by the Johns Hopkins Bloomberg School of Public Health, which contains 334 studies on vaccine effectiveness. After consolidating all the data, around 22 leading infectious disease experts from across Asia and Latin America were consulted to review the data, and the findings were then published in a peer-reviewed journal.
According to Dr. Anna Ong-Lim from the University of the Philippines and a member of the Technical Advisory Group of the Department of Health, the study was conducted because there was a need to better understand how well boosters work and how safe they are based on a broad range of settings and using various vaccine platforms and also looked at outcomes during the Omicron period, which started last year and up to year 2022. The focus, she added, were on the more severe outcomes or those that ended up in hospitalization and death.
“It was hoped that this information would be helpful for decision-makers, especially in this part of the world and other lower-income countries where there are so many limitations on supplies and access,” Dr. Ong-Lim said during an international roundtable discussion titled “Understanding Covid-19 vaccine effectiveness” organized by the Philippine College of Physicians, together with the Chiang Mai University Faculty of Public Health and the Indonesian Society of Respirology.
Efficacy vs. Effectiveness
Many people, Dr. Ong-Lim said, think that the terms efficacy and effectiveness are the same but they are entirely different concepts. Efficacy is about outcomes determined during a clinical trial, which means there is tight control on the number of people involved in the process, and a strict vaccine schedule.
“The data from a clinical trial is critical when seeking regulators’ approval, whose view is to make sure that the formulations are safe and work as they are claimed to be working, before they are used on the general public,” she explained.
With regards to effectiveness, this happens more in a real-world setting, she said. This is done outside of clinical trials working on a broad population demographics, with various schedules and intervals. Despite providing less-controlled data, its value is really to monitor how the vaccines work in a realistic scenario.
Are vaccines really effective?
Though the study contained a lot of data, Dr. Ong-Lim said they just highlighted three specific points. One, all boosted Covid-19 vaccines showed high effectiveness against Omicron-related severe disease and death in the elderly as well as the general population. She said they looked at around 52 studies, and about 252 data points were compiled, where the first group looked at the impact of the vaccines on the general population and compared that to elderly people at over 60 years of age. Regardless of the platform used, the effectiveness for the two groups was quite high (84.2 percent for the general population and 87.4 percent for the elderly) in terms of protection against severe disease and death.
Also, the study showed that all studied homologous vaccine schedules are as effective as one another at protecting people against Omicron-related severe disease and death. “This is another reassuring piece of information. Whatever vaccine an individual receives, whether an mRNA or inactivated platform for primary and boosters of the homologous (same vaccine brand) vaccine, vaccine efficacy ranges from a low of 75.8 percent, to a high of 91.1 percent.”
Finally, even those who received heterologous or mixed (different vaccine brands) schedule of vaccines, vaccine efficacy registered were mostly on the mid-80 percent efficacy to as high as 98-percent efficacy.
Length of vaccines’ effectivity
Dr. Ong-Lim said there are lot of concerns whether the vaccines’ effectiveness is durable so there were a lot of worries. She said the effectiveness of the current vaccines in preventing infections and mild symptoms drop off pretty quickly in the first three months after booster vaccination to as low as 31 percent.
“But what’s reassuring is that for severe disease, which is the outcome we are trying to prevent when the vaccines were formulated, the level of protection was quite impressive and persists for a long period of time, retained for three months and beyond,” she said.
Dr. Bruce Mungall from AstraZeneca, on the other hand, emphasized the risk-benefits balance of vaccines, particularly in protecting against severe outcomes. He said various studies on safety aside from effectiveness were made to study adverse effects of multiple vaccines. The studies showed that the risk of adverse events is generally lower with a second dose of the vaccine. “As more studies come through, what we are looking at are they are just as low when it comes to the third dose. These means we are not seeing any additional cumulative risks thus far. If we can prevent Covid-19 from even happening through vaccination, we can also prevent many of these risks from happening as well.”
As for the level of protection provided by AstraZeneca’s vaccines, Dr. Mungall said that boosting with AstraZeneca’s vaccine and mRNA Covid-19 vaccines provide equally high protection against Omicron-related severe outcomes, including hospitalization and death, even as new subvariants of the virus emerge.
A newly published review showed that any three-dose schedule including the AstraZeneca vaccine was highly effective at protecting against severe Omicron outcomes (84.8 percent to 89.2 percent). The review further concluded that a fourth dose booster is likely to add a significant level of additional protection, with a recent real-world study from Asia demonstrating no cases of severe outcomes due to Omicron in people vaccinated with a fourth dose of either the AstraZeneca vaccine or a mRNA Covid-19 vaccine from February to April 2022.
Dr. Rontgene Solante, one of the review’s authors, said: “Current vaccines are still effective in protecting the vulnerable populations. Instead of focusing our resources on getting variant specific booster vaccines, it is important that all governments and all countries will focus on how to increase vaccination coverage and how to increase uptake of booster vaccination in the population.”
Professor Guy Thwaites, Director of the Oxford Clinical Research Unit in Vietnam and one of the study’s authors said: “Booster dose data is critical for informing ongoing vaccination strategies as we transition from pandemic to endemic, whether that is an annual vaccine for most people, or every six months for those considered to be more vulnerable. This expert review of data can reassure governments and the public that viral vector and mRNA Covid- 19 vaccines offer great booster protection against serious outcomes in the ongoing battle against Omicron, particularly because that protection also shows very little sign of waning, even after a three-month period.”
AstraZeneca’s vaccine is a “viral vector” vaccine, which means a version of a virus that cannot cause disease is used as part of the vaccine, so if the body is exposed to the real virus later it is able to fight it. This vaccine technology has been used by scientists over the past 40 years to fight other infectious diseases such as the flu, Zika, Ebola and HIV.
AstraZeneca and its global partners have released over three billion vaccine doses to more than 180 countries, and approximately two-thirds of these doses have been delivered to low- and lower-middle-income countries. The vaccine is estimated to have helped save over six million lives during the first 12 months of use since December 2020.
Image credits: Nonie Reyes