What Is Herd Immunity and When Will the Philippines Achieve It?

Now that the vaccine is here, we can talk about herd immunity.

This time last year when COVID-19 was still a relatively new word flashing in every headline, herd immunity was being brought up as a possible alternative to lockdowns. The idea shot down quickly. As epidemiologists have discussed before, the only time to talk about herd immunity is when a vaccine is ready and not one second later.  

Now that a vaccine is here, what exactly is herd immunity and how will the Philippines achieve it?

What is herd immunity?

Herd immunity occurs when enough people are immune to a virus that they can no longer become carriers of the virus and spread it to other people. It can occur when the majority of the population has been infected with the virus and developed antibodies to it, or when the majority of the population has been vaccinated against the virus and can no longer be carriers.

In short, herd immunity ensures that the virus essentially has nowhere else to go and can no longer spread and infect other people.

While most of the world relied on lockdowns and social distancing to battle COVID-19, Sweden used herd immunity as its coronavirus strategy. It’s a strategy that has drawn global criticism as Sweden now has the highest mortality rate among its Scandinavian neighbors. According to Australian epidemiologist Giden Meyerowitz-Katz, discussing herd immunity as a preventative measure before we have a vaccine is “simply wrong.”

But now that the vaccine is here, herd immunity is now a goal for every government health agency around the world.

How do we achieve herd immunity?

In order to achieve herd immunity in the Philippines, the majority of the Filipino population needs to be immune. This will happen through vaccination. The estimated threshold for herd immunity is said to be 70 percent, meaning 70 percent of Filipinos need to be vaccinated in order to achieve herd immunity.

According to Dr. Beverly Ho, a director at the Department of Health, herd immunity is being tackled with a three-level process by the Philippines’ health sector. Herd immunity can’t be achieved overnight. Instead, it must go through three tiers, so to speak, to achieve an immune population. According to Ho, the DOH’s first goal is to preserve the healthcare system so that it doesn’t collapse. This is where quarantines are most effective. An overflow of severe cases in hospital ERs and ICUs could damage the healthcare system, which already takes care of millions of patients with COVID and non-COVID cases.

DOH’s next goal is to radically decrease the morbidity and mortality of the COVID-19 virus. By preventing the spread of the virus through actions like social distancing, we prevent the virus from reaching the elderly or those with co-morbidities who could potentially die from the virus.

Once both goals have been achieved, the next goal is herd immunity, which can be achieved through vaccinations. In order for vaccinations to work, you need a functioning healthcare system to distribute the virus and a healthy populace to receive it.

How many people need to be vaccinated in order to achieve herd immunity?

According to Ho, the estimated herd immunity threshold for COVID-19 is currently at 70 percent. That means 70 percent of the population needs to receive the vaccine to stop the virus’ spread so it has nowhere else to go.


However, Filipinos have expressed their reluctance to receive the COVID-19 vaccine. Whether due to the impact of the Dengvaxia controversy or the country of origin of certain vaccines, only 46 percent of Filipinos want a vaccine, according to the Social Weather Station.

In an interview with Summit Media, Ho addressed these concerns by reciting a popular quote among doctors today: “The best vaccine is the one in your arm.” She also reiterated that the efficacy of vaccines in the market when it comes to severe COVID cases is all almost 90 percent or above. Ho explains that while efficacy can vary in medium cases, which is essentially similar to the flu, almost all vaccines are effective when it comes to severe cases of COVID, which can result in death.

“When we talk about herd immunity, there has to be a percentage of the population that needs to have the ability to combat the infection. We're talking about immunity to fight the infection such that when you have selected groups of people who won’t be able to get the vaccine, they will be protected,” explained Ho.

These individuals include children, pregnant and breastfeeding women, and people with extreme allergies, underlying conditions, and a compromised immune system. This essentially covers all persons with HIV/AIDS, immune diseases, transplant patients, and cancer patients taking immunosuppressive medicine.

Herd immunity acts as a shield for the individuals who are not qualified to receive the vaccine and are thus not as protected.

When will we achieve herd immunity?

It depends on how fast we can roll out the virus. As it is, it looks like it won’t be until late 2022 or early 2023 when we achieve herd immunity, according to the DOH.

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Anri Ichimura
Section Editor, Esquire Philippines
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