An illustration shows vials of a COVID-19 vaccine and syringes with the logos of US pharmaceutical company Pfizer and German partner BioNTech. Photo: AFP

More than 12,400 in Israel were reportedly infected after accepting Pfizer's COVID-19 vaccine, which led to doubts over the vaccine's efficacy, despite the reported 95 percent efficacy in Phase III clinical trials.  

This can be a sign that the vaccine's efficacy is not necessarily the same as data from experiments, which is affected by many elements such as the experiment environment and the population tested on, some experts said.   

More importantly, experts warned that a vaccine is not a panacea. The public should learn that the most effective way is wearing masks and protective suits, they said.

Israel's health ministry tested 189,000 people after they received Pfizer's vaccine and 6.6 percent of the people, including 69 who had received two shots, still tested positive for COVID-19, according to media reports.

A single dose of Pfizer's COVID-19 vaccine appeared "less effective than we had thought," and also lower than Pfizer had suggested, Israeli coronavirus commissioner Nachman Ash previously told media on Tuesday. 

Pfizer said that a single dose of its vaccine is about 52 percent effective, media reported. 

The Israeli government earlier announced a plan to vaccinate 5.2 out of its nine million residents by March. As of Tuesday, more than two million have been vaccinated, local media reported. 

Feng Duojia, president of the China Vaccine Industry Association, told the Global Times on Thursday that it is possible that vaccine recipients got infected before they developed immunity. 

Instead of preventing recipients completely from infections, the key functions of vaccination are to reduce the incidence rate or prevent recipients from getting serious symptoms, Feng explained.

Normally it takes 14 days for vaccines to build effective immunity in recipients' bodies. 

According to media reports, within two weeks after the first dose, recipients in Israel show similar infection rates as those who have not received shots. But those vaccinated started to show 33 percent fewer new infections than the others after the second dose.

The difference between a real world and experimental environment, such as the scale of the participants and whether the recipients continue wearing masks after injections, could also lead to inconformity in results, according to experts reached by the Global Times.   

Any vaccine, after being approved for use, will go through further evaluation which is dubbed as "Phase IV clinical trials" on masses of people who receive it to further study the safety and efficacy, according to Feng.  

The most effective way to prevent coronavirus infections is still physical protective measures, like wearing masks and protective suits, experts noted.

Some countries rely on vaccines as a life saver as they had tried all other measures but failed. But a vaccine is not a panacea, experts said.